Bass Trombone
A low trombone with a wide bore, usually fitted with a valve for a fourth lower.
What it means
The bass trombone is the lowest commonly used member of the trombone family. It has a wider bore than the tenor trombone and is usually fitted with one or two valves that extend the range downward and shorten certain slide positions.
The valve makes low notes accessible that would otherwise require very long, impractical slide positions on a plain slide trombone.
Musical use
The bass trombone is a standard part of the symphonic brass section, where it rounds out the trombone choir below two tenor trombones, as well as of the big band and concert band. It often carries the bass line in chorale-style brass writing or supports the tuba.
It should be distinguished from the historical contrabass trombone, pitched still lower and rare today, and from the tenor trombone, whose range ends without a valve.
Performance practice
If you play bass trombone, get used early to coordinating slide and valve: some low notes are only reachable by pressing the valve while taking the matching slide position. Aim for a firm but controlled attack so the low register doesn't sound unsteady.