As a youngster learning to play trombone we were warned not to let our cheeks expand when we played or we would end up like Dzzy Gillespie, (a famous jazz trumpet player - see attached photo). Clearly he has way more mouthfill volume than typical. This might help with FRC equalization at depth. Seems excercise to expand mouthfill volume would be to blow hard into expaned cheeks regularly. Cheers Wes

