Trombone triggers are primarily but not exclusively[REF] installed on the F-trigger, bass, and contrabass trombones[REF] to alter the length of tubing, thus making certain ranges and pitches more accessible.
A euphonium occasionally has a trigger on valves other than 2 (especially 3), although many professional quality euphoniums, and indeed other brass band instruments, have a trigger for the main tuning slide [REF].