The bass trombone is actually just a slightly larger tenor trombone. Like this, it is tuned in Bb, so it has the same tube length and differs from it only in a further bore (about 14.30 to 14.89 mm), a larger bell and a mostly slightly larger mouthpiece. As a result, it speaks better in the lower register, sounds fuller and can be played louder. The high register sounds duller and requires more effort. The bass trombone is usually not transposed in the bass clef.