From Academic Kids
The tromboon is a musical instrument made up of the reed and bocal of the bassoon attached to the body of a trombone instead of the trombone mouthpiece. The name of the instrument is a portmanteau of "trombone" and "bassoon". The sound quality of the instrument is best described as comical. This instrument is called for in the scores of P. D. Q. Bach in his oratorio The Seasonings as well as the Serenude (for devious instruments).