A Trombone is a musical instrument from Earth that is a member of the brass family. Like all brass instruments, sound is produced when the player’s vibrating lips cause the air column inside the instrument to vibrate. The trombone is usually characterized by a telescopic slide, which a player uses to change the pitches by varying the length of the tube. The trombone was most often associated with jazz music.
Starfleet officer William T. Riker was a proficient trombonist who would often join other Enterprise musicians in playing for the crew. Despite his proficiency, he had a great deal of difficulty with the song Nightbird. (TNG episode: "Second Chances")
When the Jarada of the hive Zel learned that Riker was an accomplished musician, they invited him to meet with the most prominent musicians of their society. Before the meeting was disrupted, Riker demonstrated the trombone to these musicians. Because Jaradan music did not use a single melody, the musicians felt that the trombone was somewhat simplistic. (TNG novel: Imbalance)