Crook sets are a cost-effective alternative to one-piece crooks. A crook is composed of a base body combined with a partial crook. As such it can be used just like a one-piece crook on the 3-hole short form trumpet. By replacing the partial crook, further keys can be achieved. Thus, the 440 Hz, 430 Hz and 415 Hz keys can be played with the identical base body, only the respective partial crook is exchanged.