trm, If I was you, I would do the following: 1. Limit your daily routine (when there is a 4h rehearsal) to the minimum. Dokschitzer in his Trumpet book gives suggestion for different routines in different kind of days - rehearsal or concert/gig days, practice days etc - use your common sense 2. Minimize pressure during rehearsals - make your playing more efficient, though 4 hours is serious time to test stamina and endurance. Save your face as much as possible. Remember that if your section plays well in tune it may sound louder than you may think. 3. Tell your MD if you need help with the first chair - sharing the chair may be not as glorious, but may make your music making more enjoyable and secure. You told us nothing about your situation and background: 1.Symphony? Concert Band? Brass Band? Anything else? 2. High School? College? Professional? Amateur? Then...don't forget that local help will be always much more helpful than internet - a teacher can see what you are actually doing and give you more precise instructions and more likely to see if anything is going wrong.