The Tremulant device is a harmonic tremolo Max for Live audio effect.
With this effect, an LFO is used to modulate the audio levels of 2 filters – a highpass and lowpass, with a notch at the center frequency. The output has a distinctive sound, obviously not the same as a volume modulating tremolo.
The device also has some additional noise in the modulation, and allows one channel to be flipped, creating a stereo effect.
Designed to be used with single instruments, but experiment!