Yeah, the opening makes it sound as though you are going to be writing about a particular performance, but then you end up talking about your general enjoyment of the band. You'll probably need to add a sentence or two connecting the two parts more solidly, then work on cutting down the overall word count to less than 150. Or, you could just cut the first half completely and work on adding a new intro. The heart of your essay is this:
remember the ease with which I been accepted into the band family and the trust we had in one another to always give our best. I remember my awe at hearing Jen Cho play her piccolo solo flawlessly or watching Jared march in perfect time, his tuba held high. I'm proud of having had the chance to learn, work, and march alongside them and others. If I close my eyes, I see our teal-and-white ensemble moving in unison-and myself, a part of something larger than myself.
This is what you should definitely keep and build on. You are very detailed and descriptive here, and you take a fairly original approach, focusing not so much on the musical aspects of band as the social ones.