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This is a picture of a trombone with its different parts identified: Bell, Slide, Mouthpiece, Water Key, and End Button.http://puffincat.blogspot.com/2008/01/learn-trombone-with-shane.html

Tommy Dorsey played the trombone.  The trombone is a member of the brass family , meaning it is made out of metal and wind is used to make it sound.  The trombone has 3 main parts, the bell, which vibrates to amplify sound, the slide, which allows the player to switch pitch, and the mouthpiece that connects the player to the instrument and is the beginning place of sound.