Non-tonal percussions are usually controllable in two ways:
• From the manuals (usually the Accompaniment) and Pedal to provide a rhythmic backing (eg the castanets in a tango or the cymbal in a march)
• From toe pistons or other controls to provide accents or effects (eg the Triangle to accentuate a phrasing or the Bass Drum and Crash Cymbal to provide a grand crash).
The instruments are struck by mallets or beaters attached to pneumatic motors. Percussions such as the snare drum roll or cymbal roll have contacts on the mallet (after the fashion of a door-bell) to give the re-iterating beat which simulates the roll.
Typical non-tonal percussions include:
Bass Drum Roll Snare Drum Roll Cymbal Tap Cymbal Roll Cymbal Crash
Bass Drum Roll
Snare Drum Roll
Such non-tonal percussions are colloquially known as ‘Traps’, considered to be a dance-band expression for a drum-kit.