Ok so basically I tried to write about teamwork but this sounds more like I'm talking about music, and I'm not sure which way I should go , because I really like the bit about music but really I value teamwork:
The unity of making music with an ensemble is the greatest joy of playing flute. Together, we paint pictures of the Grand Canyon, evoke sounds of the great Moldau river, or celebrate with a Festive Overture. Band has taught me the valuable lesson of teamwork ever since I joined in the 4th grade. We must learn our parts and listen to each other, all while watching the conductor. When the sound of my flute interweaves with the rest of the band to create ringing harmonies, I almost shiver with delight. The fact that I am part of the creation of such beautiful sounds captivates me.
I wouldn't be able to enjoy the pleasure of music without my fellow musicians, whom I've relished meeting and working with towards the common goal of a perfected piece. These are friends that I will cherish throughout my life and that I could have only met in band. The bonds of teamwork that are created through such groups like band matter to me the most in this world. Science Olympiad, Green School, all these activities depend on teamwork. Each member is given a responsibility and must trust the others to do their own. I love that we depend on each other and grow closer as a team. I value teamwork above all because the members will always back me up, whether we succeed or not.
When the sound of my flute interweaves with the rest of the band to create ringing harmonies
Incorrect modifiers here. "sound" can not be compared with "the rest of the band"
Generally, I think it's good. I like the way you describe your role in playing music and your thought of teamwork. My suggestion is you may try elaborating more about you (how you unite with other members) and making less generalization (especially in the last 3-4 sentences).
Good luck with your essay!