Trombones have a telescoping slide mechanism that varies the length of the instrument to change the pitch. However, many modern trombone models also use a valve attachment to lower the pitch of the instrument. The tenor trombone is a non-transposing instrument pitched in B♭, an octave below the B♭ trumpet. The once common E♭ alto trombone became less widely used as improvements in technique extended the upper range of the tenor, but it is now re-surging due to its lighter sonority which is appreciated in many classical and early romantic works.
