The modern trombone has a slide which the player moves to different positions to produce the notes. The slide is U-shaped, and when it is moved it alters the length of tubing that the ait travels through, and therefore changes the pitch of the note. The longer the tubing, the lower the note. The lips are also tightened to produce higher or lower notes.
Although there used to be many types of trombone, nowadays the B flat is by far the most common.
