Tremulant
The tremulant (from Latin tremulus "trembling") is a device in the organ that periodically varies the air flow ( wind ) and thereby creates a tremolo .
Sound effect
The (loud) strength of the sound is changed - it begins to vibrate or tremble - and only to a lesser extent does the pitch change periodically ( vibrato ). The tremulant is mainly used to emphasize a single voice, often the cantus firmus , against the accompanying voices .
Beat registers and the rotary effects of the electronic organ (see Leslie ) have comparable sonic effects .
Designs
Channel tremulant
One possible design is the channel tremulant, in which a resilient wooden or leather flap built into the wind tunnel causes the wind to vibrate. Dom Bedos calls this variant tremblant doux .
Seesaw spring tremulant
The seesaw spring tremulant works through a bellows placed on the wind tunnel, which vibrates through the bounce of a weight on a valve attached to the top of the bellows.
Valve tremulant
The most commonly built tremulant is the valve tremulant, it works with a valve relay. After switching on (electrical, pneumatic or electro-pneumatic) three cone valves lift one after the other; the previous one opens the wind supply for the next; the last valve opens the wind supply to a small tremulant bellows, which periodically allows blasts of air to escape from the wind tunnel.
Shock tremulant
If the wind is stabilized by a float bellows, this bellows can also be influenced by a shock tremulant. The periodically generated shocks, which are usually produced by an electric motor, are then transmitted mechanically to the float plate. Such a pressure-increasing tremulant can usually be regulated in speed from the gaming table and is currently the most modern type of construction. A differently built valve tremulant can also be used as a variant: Here, periodic blasts of air are not released from the wind tunnel, but the valve tremulant sends blasts of air to a small bellows that is connected to the float plate and transfers the bumps to it.
particularities
With historical organs there are occasionally two tremulants at different, fixed speeds.
Tremulants are usually installed in such a way that they affect a single work . A tremulant for the pedals is unusual. Tremulants, which affect the entire organ, are sometimes found in small organs; they are rare in larger organs.
In cinema organs , in addition to a tremulant that affects the entire organ, there are often other tremulants that affect individual rows of pipes and thus all of the registers generated from these rows of pipes.
