Groove Analogizer ($29), a Windows VST effects plug-in from Luigi Felici of NUSofting, is a percussion-oriented synth with drum sounds that you trigger using envelope followers rather than playing directly. You can insert Groove Analogizer in either an audio or a virtual-instrument track. It is most flexible when you use it to process a drum synth or a sequencer (see Web Clip 1).
Groove Analogizer's control panel tells the whole story: there are three identical channels, each containing an envelope follower and an oscillator geared to synthesizing percussion sounds. The envelope follower incorporates a bandpass filter for limiting the frequency range that triggers the channel. The trigger signal can also be limited to either side of the stereo input, and a sensitivity knob gives you further control over triggering. For example, you could set up two channels with different inputs, each of which triggers on only snare-drum hits, but with one channel triggering on every hit while the other triggers on only loud hits.
Each oscillator has a single release envelope that controls amplitude. Optionally, you can also apply it to pitch to affect positive or negative pitch bend. The release-envelope amount tracks the envelope follower, meaning that louder incoming notes result in more envelope modulation. The oscillator's Timbre knob controls the mix of noise with the oscillator's waveform. You can vary the waveform from a sine wave to what sounds like a narrow-band pulse, and the oscillator can modulate its own frequency for even greater harmonic content.
Each Groove Analogizer channel has controls for volume, pan, and a prevolume send to a global stereo feedback-delay line. You can slightly offset the left and right delays using the Stereo Offset slider, and the delay line has its own volume control. Instead of a wet/dry control, the plug-in has separate faders for the wet and dry signals.
As with many envelope-follower effects, setting up Groove Analogizer to follow a drum groove can be a bit touchy, but it's well worth the effort for the spice it can add to a basic drum track. You can download a save-disabled, time-limited demo from the NUSofting Web site (http://nusofting.liqihsynth.com).