Crystal is a new, free, modular synth VSTi for MacOS featuring both subtractive synthesis and frequency modulation (FM) synthesis. It offers abundant modulation control with over 60 parameters which may be modulated, multi-stage envelopes with graphical editors, extensive tempo sync of envelopes/LFO rates/delay times, built-in effects for chorus/flanging/comb filtering/echoes, and a band splitter for effects processing by frequency band.