Many players of wind instruments talk of the perceived importance of the shape of the mouth on the sound. In the case of the didjeridu, the effect on the timbre is so clear as to be incontestable. Among scientists, however, there is considerable variation in opinion about the effect on pitch [1- 4]. In this paper we report experiments on well-characterised model systems: artificial wind instrument players. Using plausible values of the relevant parameters, these show that vocal tract shapes can have important effects on both pitch and timbre.
Many brass performers and teachers, including myself, have cited Bernoulli’s principle as assisting the air speed as it strikes the vibrating lips for the importance of tongue position while playing. I’ve asked some physics teachers and engineers about this and almost all of them, with some exceptions, have suggested that this might be true. That said, this presentation was focused on the vocal tract impedance (if I understand this correctly, that is how the shape of the vocal tract influence pitch and timbre of a particular pitch).
On the didjeridu the influence was quite strong, perhaps in part due to the larger bore size of the instrument and the much larger vibrating area (there are a lot more of the lips inside the “mouthpiece” of the didjeridu than inside a trombone mouthpiece). They did note that it was an influence on the trombone, however.
The shift in pitch, over the range studied, is typically 20cents: a musically important effect for intonation. Preliminary measurements on experienced brass players showed a comparable shift in pitch when they were asked to lower the tongue, keeping all else constant.
They also noted that a change in tongue position can “cause a transition between different playing register.” In other words, you can shift tongue position and change partials on a brass instrument.
This has some interesting implications for brass performers and teachers. Some folks swear that they keep their tongue position consistent, regardless of what register they play in. This view is in the minority and I suspect that players who claim this aren’t even aware of their shifting tongue position. That said, different people are going to have variations in the size and shape of their mouth and tongue and it would be interesting to compare those players. I’m also curious about the difference between different traditional brass instruments. Do trumpet players change the position of their tongue more or less than tuba players?
Regardless, I think that research like this suggests that tongue position is an important part of playing in tune and with a focused tone on a brass instrument. Players and teachers dealing with intonation issues or poor tone may want to investigate what is happening with the tongue position and work out practice approaches that can help a player learn how to achieve an optimal tongue position according to the register being played.
Here’s a lengthy video by trumpet player Charlie Porter on how to form a brass embouchure.
I have had some disagreements with Porter in the past. I have some quibbles with some of his instructions too, but I like his recommendation to set firm the lips up before setting the mouthpiece on the lips. Two of the other steps he recommends (pulling the lips open after setting the mouthpiece and wetting the lip center with the tongue after that) I feel would risk undoing the value of firming before setting.
Watching through the video I didn’t understand if he was suggesting the embouchure aperture remains open throughout the lip vibration, so I asked him about it. He was kind enough to take the time to clarify for me.
Of course the lips rapidly close and open during vibration. That’s not the point…I’m not arguing that they they never close briefly, per each vibration occurring…the point is that players are often way too tight and begin with closed lips and press them together to the point of distorting the vibration.
It’s a rather long video, but take look at it if you’re interested in different thoughts about setting the embouchure formation for playing.
The idea of students having a “learning style” refers to a concept that that individuals differ on how the best learn, develop, and retain information. For example, someone who is considered to be a “visual” learner needs to see the information in some way, while an “aural” learner will want to hear it explained. On its surface this seems like a good thing, since we are all individuals and experienced teachers develop strategies to help students with different needs and backgrounds learn better. Unfortunately, the idea of catering lessons to a particular student’s learning style doesn’t show that it actually helps. In fact, it can even leave some students behind when proven methods of instruction are avoided in favor of what essentially amounts to a preference on the student’s part. Teachers end up working with a student’s strengths and not addressing the weaknesses.
In spite of the lack of evidence to back up the learning styles theory, this is a pervasive myth among educators, students, and the general public. Companies that want to sell lesson plans and other educational support materials to schools and teachers are, in part, to blame for the continued belief in this myth. Here’s one example that purports to tell you your learning style by asking you 20 questions. I tried it out and learned that I was an “auditory” learner.
If you are an auditory learner, you learn by hearing and listening. You understand and remember things you have heard. You store information by the way it sounds, and you have an easier time understanding spoken instructions than written ones. You often learn by reading out loud because you have to hear it or speak it in order to know it.
As an auditory learner, you probably hum or talk to yourself or others if you become bored. People may think you are not paying attention, even though you may be hearing and understanding everything being said.
Here are some things that auditory learners like you can do to learn better.
Sit where you can hear.
Have your hearing checked on a regular basis.
Use flashcards to learn new words; read them out loud.
Read stories, assignments, or directions out loud.
Record yourself spelling words and then listen to the recording.
Have test questions read to you out loud.
Study new material by reading it out loud.
Remember that you need to hear things, not just see things, in order to learn well.
The problem with assessing a student’s learning style with questions like this survey is that it doesn’t actually address learning. Asking someone the “best way to study for a test” doesn’t offer information on how a student best learns because it doesn’t assess whether the student did well on the test! The only way to assess whether learning styles are helpful is how well they learned the material, not what someone prefers to do for fun or what strategies they want to try.
Another online “test” (I won’t link because it wants you to register before it gives you results) is a bit more thorough one that has some more nuance to the questions and asks more, but again, I find many of the questions odd (“You have a good sense of color” “You hear small things that others don’t” – can a so-called visual learner be color blind or can someone with some hearing loss still be a so-called aural learner?) and none of the questions assess learning.
A good summary of why learning styles is a myth can be found in this Wired article.
Convincing evidence for learning styles would show that people of one preferred learning style learned better when taught material in their favored way, whereas a different group with a different preference learned the same material better when taught in their favored fashion. Yet surprisingly few studies of this format have produced supporting evidence for learning styles; far more evidence (such as this study) runs counter to the myth. What often happens is that both groups perform better when taught by one particular style. This makes sense because although each of us is unique, usually the most effective way for us to learn is based not on our individual preferences but on the nature of the material we’re being taught – just try learning French grammar pictorially, or learning geometry purely verbally.
Teaching children according to their individual “learning style” does not achieve better results and should be ditched by schools in favour of evidence-based practice, according to leading scientists.
Thirty eminent academics from the worlds of neuroscience, education and psychology have signed a letter to the Guardian voicing their concern about the popularity of the learning style approach among some teachers.
What about all that literature that supposedly supports learning styles? Harold Pashler, Mark McDaniel, Doug Rohrer, and Robert Bjork wrote a review of the literature.
Our review of the literature disclosed ample evidence that children and adults will, if asked, express preferences about how they prefer information to be presented to them. There is also plentiful evidence arguing that people differ in the degree to which they have some fairly specific apti- tudes for different kinds of thinking and for processing different types of information. However, we found virtu- ally no evidence for the interaction pattern mentioned above, which was judged to be a precondition for vali- dating the educational applications of learning styles. Al- though the literature on learning styles is enormous, very few studies have even used an experimental methodology capable of testing the validity of learning styles applied to education. Moreover, of those that did use an appropriate method, several found results that flatly contradict the popular meshing hypothesis.
Searching online for evidence that both supports and refutes the theory of learning styles shows a general difference between those supporting and those debunking. Sites and “articles” that support learning styles tend to lack citations and when they do have them, the studies listed either are from companies that want to sell their materials to teachers, are poorly done, or even state the exact opposite of what that source is claiming. On the other hand, criticisms of learning styles tend to be well researched with peer reviewed articles from reputable authors and journals and provide a much more nuanced view of teaching and learning.
The bottom line for teachers is that while we can and should use every tool available when necessary, it’s important to look at the bigger picture – whether learning is taking place and whether the results we’re getting from our students is what they are truly capable of. By all means, reinforce the students’ strengths, but address their weaknesses too.
A thread on the Facebook Trombone Pedagogy group lately has been discussing different thoughts on coordinating breathing with setting the embouchure and placing the mouthpiece. I thought I’d take this opportunity to discuss my preferred way of teaching students to coordinate air and embouchure together, based on Donald Reinhardt’s instructions from his writings, including his Encyclopedia of the Pivot System.
While the jaw is in its playing position, form the saturated embouchure with ALMOST buzzing firmness, so that the lips are “just touching” at the vibrating points. When in doubt, form the lips as if to buzz. . .
Place the mouthpiece upon the embouchure formation as just prescribed and use sufficient “contact pressure” to locate and sustain its position in the playing groove of the embouchure. The actually placement must be executed in accordance with the [embouchure] type. . .
Inhale the high-pitched, whispered “IM” (not “OM” or “UM”) through both mouthcorners – NEVER THE MOUTHCENTER – simultaneously. . . In short, eliminate “gear shifting” and inhale with a minimum of embouchure distortion.
At it’s heart, Reinhardt’s advice is to work towards unifying the player’s pre-playing sensations with the playing sensations. In other words, he felt it was valuable to have as little change as possible in the position of the lips and mouthpiece upon the lips from inhaling to playing. In order to encourage this, he instructed his students to practice (during certain exercises – not during rehearsing and performance) to firm the lips as if buzzing first, place the mouthpiece on the firmed lips, inhale through the mouth corners while maintaining mouthpiece pressure and holding the lip center just touching, then commence blowing by coordinating the mouth corners snapping into their correct position. Taking breaths in the middle of phrases is to be simply a matter of continuing to breathe through the mouth corners while keeping everything under the mouthpiece rim and inside the mouthpiece should remain more or less in playing position.
Many players, including some excellent ones, either don’t consider their embouchure when breathing or are so focused on moving lots of air that they don’t feel that minimizing the embouchure “gear shift” between inhaling and blowing is valuable. Some players will open their mouth very wide to inhale and the mouthpiece placement shifts slightly every time they begin blowing. Some players will set the mouthpiece on relaxed lips and firm them only just as they begin blowing, which can result in twisting or winding the lips up under the rim or distortions and inconsistency in their overall embouchure formation from breath to breath. Consistency in a player’s embouchure formation should result in better playing consistency.
One of the biggest challenges to adopting this approach is that it’s difficult to take in as much air as quickly when you’re only breathing through the mouth corners. Trumpet and horn players may find the smaller mouthpiece size makes keeping the lip center just touching inside the mouthpiece while inhaling to be easier than low brass players with their larger mouthpieces. I think it’s important to keep in mind that this approach is meant to be practiced only at specific times in your routine and then forgotten about while you move on or are performing. We can think of this approach as an ideal goal, but that not every playing situation is going to make that ideal work at every moment. By aiming towards the ideal in your practice you are minimizing the potential for this to cause issues, both short term cracking notes from time to time or the longer term (and fortunately rarer) embouchure dysfunction that can result.
It’s common for instrumentalists to practice exercises and etudes to practice technique or expressive playing. These materials usually are never intended to be performed, but are instead done for the benefit they offer the musician. Composers can similarly practice composition exercises that aren’t intended to be heard by anyone, but help the composer get comfortable using a particular approach or get the creative juices flowing. Here’s a resource with 4 exercises.
Exercise 1: Compose Three Short One Minute Compositions
In this exercise you have two weeks to complete three short compositions. I like the idea of challenging yourself to complete something specific on a deadline. Some arranging commissions I have gotten are like this exercise, the client needs an arrangement of a specific tune by a specific date.
Exercise 1b: Compose One Composition Two Minutes Long
The details of this exercise include avoiding your compositional comfort zone. Again, it’s not an uncommon situation for a professional composer or arranger to be commissioned to write something that he or she might not take on as a personal project. It’s useful to be able to put your personal preferences aside and explore something completely different from your own style.
Exercise 2: Vocal Rhythms
Exercise 2b: Vocal Rhythms in a Foreign Language
I’ve used this idea many times. Select a text from somewhere and say it out loud rhythmically. Write out the rhythms you come up with and they can become the basis for an extended composition. As an aside, this works great with young music students to get them composing music together as a class. Ask them a question about what they did over the weekend and you might get an answer like, “Birthday parties, two in a row!”
Use these rhythms to create percussion music or add pitches to create a melody.
I love hearing about research like this done on musicians (and other artists). I wouldn’t be surprised if something similar hasn’t been done for athletics, so it’s nice to see that musicians are taking advantage of the technology too.
In this video they show the difference between an older, more experienced, pianist and a younger, less accomplished, pianist. They tracked both of their eye movements while playing a memorized piece and also sight reading. While playing the memorized pieces the experienced pianist visual range on the keyboard was much more stable and consistent than the inexperienced pianist.
The results of the experienced pianist sight reading is directly relevant to anyone sight reading. His eyes are scanning ahead of where he is playing. It also jumps between the treble clef and bass clef staves consistently. This skill of reading ahead is perhaps one of the most important things to develop for sight reading.
Nils Wogram is a jazz trombonist from Germany. He’s really a terrific player, he’s got that great combination of excellent technique paired with a lot of creativity. I was surfing YouTube and came across this fantastic solo using multiphonics.
There’s not really a good look at his chops in this video to really guess his embouchure type. It *seems* like his mouthpiece is fairly high and close to the nose, but the camera never focuses closely enough and at a good enough angle to say more than his embouchure is one of the downstream types. I did want to post that video, though, because it’s a really neat example of what someone can do with multiphonics.
There’s seems to be a lot more research done on the development of motor skills with athletics compared to music, so often times musicians will look at athletics and sports training methods for ideas on improving musical practice and pedagogy. Recently I came across a podcast called Golf Science Lab and listened to their episode, What Every Golfer Ought to Know About FOCUS with Dr Gabriele Wulf.
Where should your focus be in during a shot? Or when you’re learning how should you think about a move to make a change in the most effective way.
Although the motor skills used in golf are pretty different than those used in playing the trombone, for example, it’s not too far of a leap to assume that what applies to golf might also be useful for musical practice. Wulf says,
Performance is often enhanced immediately when I focus externally as opposed to internally, but also the learning process is facilitated when learners adopt an external focus. So learning is sped up. You reach a higher skill level sooner than you would with an internal focus.
An internal focus refers to the coordination of body movements, where an external focus is on the intended effect. In golf the examples of things that a golfer could use as an external focus were the club, the ball, the hole, even the player’s belt buckle or buttons. One of the interesting points made in the podcast were the distance effect. In other words, the further away the point of focus, the better the results. So focusing attention on club face would be better than focusing on the handle of the club because it’s a bit further away. Focusing on the ball is a bit further than the club face, but focusing on the flag or the hole would do better. Here’s the rub, the optimal distance of the focus depends on the skill level. An expert golfer would focus on the trajectory of the ball or target, but a novice would do better focusing on the club face, because they still need to practice the technique.
The tricky thing is to try to teach and practice the necessary technique with external focus. Wulf offered a golf example. Rather than telling the novice golfer to transfer his or her weight to the left foot (an internal focus), teach them to push off of the ground on the left (external focus).
What does this mean for music practice? Off the top of my head, with brass embouchure practice try taking the attention off the lips and move them on to the mouthpiece rim. When practicing breathing instead of paying attention to the feeling of the stomach and chest moving, focus on the air as it passes the lips or even visualize the air blowing across the room.
What ideas can you think of to teach musical technique in such a way as to move the focus from internal to external? How can you take that idea and make the focus even further away the more expert the musician becomes?
This week is the second (I believe, might be the third) annual Asheville Amadeus festival. The Asheville Symphony Orchestra teamed up with several other local organizations to celebrate the life and music of Mozart. There are talks, chamber music, sing-alongs, even a local brewery puts out a limited release beer called Wolfgang 1756 annually for this festival.
The most exciting part of Asheville Amadeus for me this year is the participation of the string students from MusicWorks! Asheville with the Asheville Symphony Youth Orchestra. The Asheville Symphony Orchestra is bringing in Midori in for a week long residency and she will be giving our violin students a master class too.
If you’re around western North Carolina this week looking for some Mozart related activities, consider attending some of the events around Asheville.
One of the more popular posts I’ve written here is Brass Embouchures: Playing On the Red Is Fine (as long as it fits your anatomy). In this post I tried, somewhat unsuccessfully, to point out the flaws in the nearly universal belief among brass teachers that placing the mouthpiece so that the rim contacts the vermillion of the lips is a bad thing. I will try in this post to reiterate my points more clearly.
Before going too deep into this discussion, I’ve found that it’s important to point out that I’m not making a blanket recommendation that brass players should adopt a mouthpiece placement that sets the rim right on the upper or lower lip vermillion. I’m merely pointing out that the very pointed advice to avoid it is based on faulty logic and a misunderstanding of both the anatomy of the lips and embouchure form and function. Most folks aren’t going to have the anatomical features that make such a high or low mouthpiece placement work efficiently, but some do and for these players moving the mouthpiece placement off the red can be as detrimental to their embouchure as another player moving the placement to the red when it shouldn’t be. This is something that is unique to the individual player and needs to be taken on a case by case basis.
There are three basic arguments against placing the mouthpiece on the lips so that it contacts the vermillion along the top or bottom of the rim:
A famous teacher or player advocated against it.
The anatomy of the vermillion is such that it makes it more sensitive and prone to damage than the rest of the lip.
It’s mechanically incorrect and won’t work as well as a placement with less rim contact on the vermillion.
Famous Players and Teachers
If you’re reading the post and questioning why I’m going against what appears to be conventional brass pedagogy, that’s a good thing. I always recommend that folks learn not just what we know about brass pedagogy and mechanics, but also take the time to understand how we know what we know. It’s very easy to find folks who actively discourage placing the mouthpiece on the red of the lips, but it’s not easy to understand why they recommend that. Many of these folks make their case using arguments 2 or 3 above, but an awful lot simply assert without evidence.
The bottom line here is that we can’t simply take a statement at face value based on how famous the person is who said it, we need to look past that and deal with the evidence. That which is stated without evidence can also be dismissed without evidence.
There is an awful lot of misinformation and misunderstanding about the anatomy and histology of the lips in the brass literature. Here is one example:
To function properly, the inner edge of the mouthpiece must be placed on tissue that is supported by muscle, but the lips are composed of fatty tissue that by itself cannot support a normal embouchure.
-Frank Campos, Trumpet Technique, 2005
Part of the difficulty in parsing comments like Campos’s is that while the medical literature has a very precise definition of the lips (which runs all the way up to the nose and down to the chin), many brass authors use the term “lips” to refer to just the vermillion. Regardless of the exact meaning in the statement above, it’s demonstrably incorrect. The entire lip, including under the vermillion, is internally made up of the orbicularis oris muscle group. There absolutely is muscle under the vermillion. Be careful when you look at diagrams that draw in the vermillion as a point of reference, they are misleading. Here is one diagram that leaves out the vermillion as a reference.
Another, less common, point I’ve recently come across is that because the epidermis at the vermillion is thinner than the normal epidermal layer there is less cushion from the skin:
Lips have around 3-5 cellular layers and above the vermillion border has as high as 16 cellular layers.
Since “asdfghj” is both posting anonymously and also not citing his/her source, I can’t really comment on the legitimacy of this claim, however it does seem plausible. The reason the vermillion of the lips are red in people with fairer skin is that the color of the blood vessels underneath the vermillion come through. For the sake of argument, I’ll accept this as true. I still don’t find this a compelling argument and here’s why.
Without heading over to a university library and digging through the literature, a cursory internet search shows one apparently reputable source that states, “The thickness of the epidermis varies in different types of skin; it is only .05 mm thick on the eyelids, and is 1.5 mm thick on the palms and the soles of the feet.” How does this compare to the layer of skin of the lips, both the vermillion and elsewhere? It’s hard to say for certain using the internet, but Wikipedia (take it with a grain of salt) states, “The average human skin cell is about 30 micrometers in diameter, but there are variants. A skin cell usually ranges from 25-40 micrometers (squared), depending on a variety of factors.”
Let’s use the 30 micrometers average to calculate how thick the skin of the vermillion is compared to the normal epidermal layer on the lips. If the vermillion has 4 layers, that 120 micrometers. The 16 layers of skin in the rest of the lips would make for a layer 480 micrometers, a difference of 360 micrometers, or .36 millimeters. For comparison, human hair is said to range up to 181 micrometers in diameter, so the difference here is about two layers the size of the of a human hair.
I don’t find supposed cushion of two hairs to be a compelling difference, considering the mouthpiece forces involved. It’s not the layer of skin that provides the cushion and support of the embouchure, but the muscle underneath.
All the above shows, however, that there don’t appear to be plausible reasons why the vermillion would be more sensitive to pressure. That doesn’t mean that the vermillion actually isn’t. In order to get an idea, I spend some time back in 2012 going through both the medical and musical literature to see if there was any indication that injuries to the lip occurred at the vermillion more than the rest of the lip, or to see if any medical professionals happened to comment on this specific point.
While most brass players don’t “place on the red” in such a way that the rim contact the upper or lower vermillion a great deal, 100% of brass players place the mouthpiece with at least some rim contact on the vermillion. If the vermillion was more prone to injury than the rest of the lip, I would think that the medical literature discussing lip injuries due to brass playing would indicate this. In fact, it is rarely mentioned.
Injuries to the lips due to brass playing happens where the rim happens to be on the lips, irrespective of the vermillion. It appears that the upper lip (the entire lip, not just the vermillion) is more prone to injuries than the lower lip (hence the common advice to not “dig into” the upper lip with the mouthpiece or keep more mouthpiece “weight” on the lower lip compared to the upper). Injuries can and do happen under the vermillion, but perhaps more commonly outside the vermillion (which is unsurprising, if you consider that more players are going to have the rim contact on the upper lip above the vermillion. In fact, some lip injuries happen completely away from the rim contact.
I was also able to find some literature that flat out stated that the vermillion area of the lips is not more prone to injury. H.L. Wilson, a medical doctor writing for The Clarinet, discussed the vermillion in the context of a clarinet embouchure.
In summary, the vermilion portion of lips tolerates pressure well. . .
-Wilson, H.L. (2000). Lips. The Clarinet, 27(4), 38-39.
Yes, the forces involved in a clarinet embouchure and brass embouchure are different, but combined with a more thorough understanding of the anatomy and histology of the lips along with a lack of evidence to the contrary, this leads me to believe that there is no anatomical reason to believe that it is risky to place the brass mouthpiece rim on the vermillion.
While the above discussion of anatomy is outside of my particular area of expertise, brass embouchure mechanics is right in my wheelhouse. I first became interested in brass embouchure mechanics sometime around 1996. I wrote my dissertation on original research investigating brass embouchure types and their correlation to easily observed physical characteristics. Since completing my doctorate in 2000 I’ve published and presented resources that deal with brass embouchures in a peer reviewed journal, academic papers, online, and at professional conferences. I’ve documented with photos and video around 100 brass players’ embouchures of beginning students, college students, professional performers, university brass teachers, and amateurs over five states at six different universities. I’ve been asked to consult with physical therapists and doctors treating embouchure injuries in the United States and Europe and some of my writing about brass embouchure have been translated into Japanese and Italian. Part of conducting my research involved thorough reviews of the literature, so at risk of blowing my own horn (pun intended), I’m fairly confident in the information and context I can provide here about brass mechanics.
On the other hand, we can consider whether it’s mechanically incorrect to place the mouthpiece very high or low. This feature also varies quite a bit from player to player, with most folks falling more towards the center than very high or very low. While there are many anatomical features that influence an individual brass player’s mouthpiece placement, such as the shape of the teeth and gums that provides the support structure for the embouchure, the most likely characteristics that influences the vertical placement of the mouthpiece include the length of the lips compared to the length of the teeth and gums and possibly the shape and angle of the lips to each other. The shorter the player’s upper lip, the more likely that player appears to need to place the mouthpiece lower on the lips.
As you can see in the photo to the left, my upper lip is very short in comparison to my upper teeth and gums. When I form my embouchure I have to stretch my upper lip down quite a bit in order to get it over the upper front teeth. There simply isn’t much lip mass in my upper lip that is free to vibrate inside the mouthpiece.
A vibrating brass embouchure works more like a clarinet reed than an oboe reed. One lip or another predominates inside the mouthpiece and is the primary vibrating area. The other lip does vibrate in tandem with the other, but it serves more like the clarinet mouthpiece to the other lip as the reed. This feature can be easily seen on Lloyd Leno’s films.
For me, and for a minority of other brass players, anything other than this extremely low placement doesn’t work well at all. Most folks find it too hard to play this way, but they don’t have the same extremely short upper lip. I tried for a long time to play with a more conventional looking mouthpiece placement. I was taught early to try to keep my mouthpiece centered on the lips and with more upper lip inside and so I played that way all the way into my mid-20s. My personal experience was that I played OK with the centered placement (well enough to get through two music degrees and be accepted into doctoral studies in trombone performance), but until I made the correction to my embouchure you see in the photo to the right that I did not have the range and endurance I needed to play at a high level. This embouchure type isn’t as common as more conventional looking brass embouchures, but it probably represents about 10% of brass players.
Despite the opinions of many other brass players and teachers who feel otherwise, there appears to be no anatomical or mechanical reasons why placing the mouthpiece so that the rim contacts a great deal of the vermillion is going to lead to greater risk of injury or mechanical difficulties, provided that the player’s anatomical features are best suited to that placement. Individual anatomy is so variable that even setting a “rule of thumb” is arbitrary at best and may even lead to a brass student playing in a way that is mechanically inefficient for his or her face – which does increase the risk of injury, regardless of how conventional the mouthpiece placement may look.
In my opinion, the whole idea of using the vermillion as a factor for diagnosing or troubleshooting a brass embouchure is misguided. It is much better for brass teachers and players to gain a more thorough understanding of the basic brass embouchure types and how they function, as well as how much brass embouchures vary from player to player, even between players belonging to the same embouchure type. We can probably safely ignore the advice from teachers who emphatically state that this is wrong unless and until they begin providing plausible evidence to the contrary.