QM-Synth by K.M. Krebs is a synth implementing Quantized Modulator (QM) synthesis.
Zed @ Synth Of Mine explains Quantized Modulator synthesis:
You take a simple wave (sin wave at the picture) with a frequency X (i.e. 1 / T), quantize by a frequency Y(1 / t) and use the result as FM modulator. It’s easy to see how it’s simple and *almost FM synthesis*. But the quantization makes an enormous and extraordinary difference between QM and FM synthesis.
QM-Synth, K.M. Krebs’ SynthEdit implementation of QM synthesis, can be downloaded
If you own Reaktor you will want to check out Zed’s Quantum Radio v1.0 (near the bottom of the page).