When composers write for the trombone for the first time, the pieces are often quite difficult to perform because there lacks an understanding of how the instrument works. Because of this, trombone players are often discouraged to play said new pieces. I have seen several pieces where the trombone will have impossible glissandi, insanely fast mute switches, and crazy slide positions at fast tempos. The FREE resources below will give a general understanding of how the trombone works and what a professional player can be capable of. While a lot can be achieved, it is best if the composer has a good understanding of what is possible and impossible.