While everyone thinks about what its like to play the flute, the feeling, the emotions, ect, you have to remember the experience. A good example can be picked up by anyone who has marched a good show before, all that seems to happen is you start and the next moment, you're done. When you play something at your best, you tend to forget about everything around you because you're solely focused on the music.
This has happened to me only three times in all the years I've been playing, once during a solo I had, another was the Region concert last year, and the last being just this past Tuesday at the UIL marching.
When you play with everything you've got, everything you know and have worked so hard on, every fiber of you're being seems to flow with the music. Almost as if to snatch your very soul to take it on a ride through the world as it is created from the sound you make. Music in itself is not just 'oh so beautiful' as if it were something you could touch, it just seems to fill you inside and well, happen.
Physically speaking? Well, on the marching field, you're moving so fast your heart seems to be in step with the Long Ranger, though for myself, I've found that even sitting poised in a chair puts my heart at the same tempo as the beat of the music. Palms sweating is the usual for someone not used to playing in front of a large group of people, their breaths shorter and their minds race with the usual 'what if I can't do this?' sort of thing. Those who are just seem to take it as another day, another step in the 'crystal stair' of life.
Personally, I find competitions exciting, nerve racking, heart pounding, finger flying, fun. But nothing beats hearing the cheers from everyone watching, especially when you forget they're even there.
Yep, that's my two cents. If you want any more, just ask.