Level 1 Trombone Solo: Rondo by Keith Snell found in the book Belwin master Solos
You will need 2 original copies to perform at NYSSMA. One copy for you, and a second copy for the judge to follow along with. These can be purchased here:
Rondo:
https://www.alfred.com/belwin-master-solos-volume-1-trombone/p/00-EL03542/?srsltid=AfmBOooBclOlmaWzVgTNQgFb8ihezXf6EXoqpy3VrA83qrjFLbKzAktB