Bass trombone. Nominal pitch: 13-ft E♭.

Technical description: Brass. The main slide is of a length normal for a trombone in 9-ftB♭. It is connected by a cord via two pulleys mounted on the bell section to an auxiliary slide in such a way that as the main slide is moved the auxiliary slide moves backwards half the distance that the main slide moves forwards, thus giving a correct total slide extension for an instrument in 13-ftE♭. This allows reading parts in bass clef with the normal slide positions for tenor trombone parts in tenor clef or reading parts for E♭bass in treble clef with the normal slide positions for tenor trombone parts in treble clef). Both main and auxiliary slides have stockings.