Part of the training regiment with a drum corps (and marching band), is learning to play through the center of the horn. This is something that should be focussed on heavily in band camp and early season rehearsals. By learning to play in the center, and not “on top or bottom” of pitch, among other things, leads to better endurance during long rehearsal days. If performers are trained to play in the center of pitch when the weather is “normal” (say mid 60’s to mid 70’s), and not the common tendency to play sharp, this will pay dividends when the weather becomes warmer, especially summertime with drum corps. If performers have the tendency to play sharp, and the temperature is in the 90’s, the group will definitely have a “dull” sound to them, and seemingly have less endurance through rehearsals.
Don’t severely react to the “sound” of the instrument (ensemble) as the weather gets ridiculously hot. When the tuning slide is pulled out almost all the way, the instrument WILL sound (and feel) differently. Nothing has changed with the performers or ensemble, it’s just, well, hot! Put “warm weather ears” on if you are a director, and if you’re a performer, make sure not to purposely lip the pitch down, as you will lose endurance, create bad habits, and fight the muscle memory you’ve been working to build.
Finally, keep the instrument in the shade when you can, and ALWAYS keep yourself hydrated!
Stay cool 🙂