Being a former professional trumpet player for many years, I am somewhat amused to read the comments
about brass playing on the physics list.
As to one minor point: it is quite possible to play tones in-between the harmonics, with no loss of
volume. This is practiced for air, embouchure, and tongue control. Most challenging is to lip
upward: for instance, being able to play all the pitches of the C# scale while fingering the C
scale. Easier is the reverse. This is a cute trick to play on those with perfect pitch who think
they know a few trumpet fingerings. By humming a second tone, and pinching the lip to make a third
tone, one can play a chord. Obviously done by people who have a lot of time to kill on road trips.
And don't forget circular breathing, being able to blow out through an instrument while breathing
in, most definitely not a trick.
Buzzing the lips alone, i.e., buzzing the melody of the etude, and buzzing the mouthpiece are both
practiced to strength embouchure and breath control, nonetheless these are not exactly the same as
producing a tone through the entire instrument. For instance, ask a professional trumpet player to
suddenly pull the trumpet off of his/hers lips, and the resulting lip buzz will be close to an
octave below. While we all practice for minimum mouthpiece pressure, nonetheless, in real life, we
use slight pressure to help shape the embouchure. In fact, one can test for range by asking the
student to buzz their lips upward in a glissando. Their range on the trumpet will top out at about
an octave above their lip buzz. Playing above this point can only occur if excessive mouthpiece
pressure on the embouchure is employed, and we've all seen enough scarred lips and heard enough
pinched sharp pitches as a result of this!
I have taught that the trumpet bell acts to reflect 90% of the standing wave energy back into the
trumpet, the remaining 10% of the energy goes into the tone projected into the room. This
reflection point can be modified by the hand as french horn players do resulting in a pitch change
and also a slight tonal change. The overall tone can also be modified by embouchure changes, by
tongue position changes within the mouth, and by air pressure changes. Modern trumpets 'slot' quite
well, that is, 'pop' from harmonic to harmonic, some brands such as Bach do this more sharply than
others. Of course the drawback is a slight loss of flexibility to bend the tone; almost all tones
(e.g. harmonics) on valved instruments needing to be bent in order to find the correct pitch.
While the bell mainly determines tonal characteristics, the mouthpiece and leadpipe determine
resistance. For easiest playing, the musician's resistance as determined by air pressure,
embouchure, teeth position and mouth shape, will match the horn's resistance.