No, not the tasty corn snacks that fit oh-so-snugly over your fingertips. We're talking about the actual army-issued abbreviated trumpets.
Prewitt is a bugler—and a really good one. We see him wail out on it later in the movie, and jam with Sal Anderson's band to "Re-Enlistment Blues." He's clearly got chops. However, his bugling skills haven't been rewarded: he was passed over by his old unit, spurring his transfer to Hawaii.
Unfortunately, the officers in Hawaii aren't interested in quality bugle music either. They want Prewitt to go back to his old ways and box, which Prewitt is loathe to do after accidentally blinding a friend in the ring. (Seems fair.)
Prewitt and Holmes have the following exchange when they first meet:
PREWITT: I was First Bugler for two years. The Top Kick had a friend who transferred in from another outfit. The next day he was made First Bugler over me.
HOLMES: And you asked out on account of that?
PREWITT: Maybe it ain't sensible, but that's the reason.
Maybe it ain't sensible, but it sure is symbolic: the bugle is an artistic alternative to violence. However, like with a lot of real artistic alternatives to violence, it seems to be receiving pretty short shrift. Prewitt can bugle to his heart's content, but it's not going to get Captain Holmes to be less of a jerk.
The only thing that's going to do that is physical violence, directed at one of Holmes' henchmen. So, unfortunately, the position of art and music in this world appears to be kind of undervalued and weak.