The trombone is a brass instrument, capable of producing sound that is rich and brilliant, lower than the French horn but not as low as the sound produced by a tuba. What makes the trombone unique from other brasses is its method of changing pitch. A trombone has no keys or valves; instead, trombones change pitch through use of a slide. Because the slide on a trombone is adjustable, the performer can slowly move between two different notes, hitting all the pitches in between creating an effect called a glissando. In the swing era of the mid-1920s the trombone began to be used as a solo instrument.