Practicing low range with a small mouthpiece
If you are working on the low range, consider doing the exercises you work on, on a smaller mouthpiece, or even on a smaller trombone if you play on a large bore tenor or bass trombone. Why? Well, playing a smaller mouthpiece makes it even more important to have the airflow centered in order to get the full sound. Big instruments and mouthpieces tend to be more forgiving if your embouchure and/or air flow isn´t dead on. You can test yourself: play a few notes in the low mid / low range in f on your large equipment. Now do the same with a smaller mouthpiece/trombone. Can you get the full sound out of it, or does it feels like it “locks up”? Of course, a big fff low E on a small bore horn with a 12C mouthpiece wont sound that great, but in general, you can get a quite big sound out of a small instrument with the proper air flow.
Practicing high range with a large mouthpiece
Being able to fully use the high range of the instrument, you need both strength and good technique. Working on the high range on either a large bore / bass trombone or with a larger mouthpiece than you usually use, will build up more strength than playing on smaller equipment. I am not suggesting that you play high trombone parts on larger instruments, but practicing this way makes good sense.
What you want to make sure, is that you have the full sound in the high range, not just squeaking high pitch noise out. So rather than going for the high D, high F, double high Bb hardly being able to hear what instrument you play on – settle for working on the highest range where you still have full sound and lot of overtones and slowly expand that upwards.
This is a great exercise for this purpose:
High range glissandos on trombone
Do I need to say that this goes for other brass instruments as well? Try it, you might get better… 🙂