Downloadable soft synths are popping up everywhere, but Crystal (Mac/Win) — a freeware VSTi from Green Oak (www.greenoak.com) — has several unique features that set it apart. A quick look at its user interface will tell you that Crystal is no ordinary synth. Its control panel is organized into five pages: one page for each of Crystal's three sound generators (referred to as Voices, but not to be confused with voices in the sense of polyphony), one page for its highly flexible modulation matrix, and one page for effects and output mixing. The features on those last two pages are what make Crystal unique.
Crystal's sound generators run on a single oscillator with five waveforms, including noise and a saw-pulse mix. An optional second oscillator can be switched on for frequency modulation. The oscillator section is followed by a 24 dB-per-octave lowpass filter. Both the filter and the output amplifier have nine-stage break-point envelopes, and in the case of the filter, you can set the low and high end of the envelope's range. The envelopes can also be looped to create a kind of draw-your-own LFO.
The Modulation Matrix lets you route six LFOs, two additional nine-stage envelopes, and a variety of MIDI messages to almost any Crystal parameter. The LFOs and envelopes can be synced to the host's tempo. With that much syncable modulation, Crystal is capable of a lot of motion, as many of the factory patches illustrate.
The output section consists of four feedback-delay lines with tempo-syncable delay times. What makes it unique is the complex routing available. First, a mix of the three Voices is fed into a 4-band crossover. Next, there's a separate send from each voice and each crossover band into each delay line. In short, you can devote each of the delays to a custom mix of voices and crossover frequency bands.
Hearing is believing: the MP3 file "Crystal" is made of five Crystal tracks with no other effects or sounds. While you're visiting Green Oak's Web site, check out the company's free effects plug-ins. Delayifier is especially interesting.