Caswell Knowledge (circuit designer):

“The VCO is the same affair as the Oscillation, the Boomstar, and the Omega. It’s kind of a combination of Arp®, Oberheim® and Moog® circuits (sort of a greatest hits), time-tested, very stable—very good tracking over a very large range; certain parts have to be hand selected to achieve that level of exacting performance. Editors Note: This module is a TONESTAR—its own thing—and not a 2600 clone attempt; nevertheless, the Tone☆ tugs lovingly at times on the sleeve of the 1970’s era classic.

Envelope FYI: The Tonestar Sustain control replicates the behavior of the 2600 and Odyssey: after the initial Decay, it continues to move (sink) very slowly, adding a little extra texture to the sound. It’s technically a flaw, but after digging out my Odyssey, it is for sure a desirable “quirk”, and the perfect companion to the 4072 filter (which we mistakenly titled a 4075 in the Boomstar Modular line).

Another bit of fun: The LFO is voltage controlled, so you can envelope, LFO, or otherwise modulate both the rate and the depth; the ADSR amount is also voltage controlled, so it can be manipulated by MIDI dynamics, MIDI volume, an LFO, etc. Greg
[St. Regis] has decreed that anything must be patchable to anything, so some technically wrong patchings (for example, pulse wave out to ADSR out) may often produce unexpectedly interesting, x-mod/notch filtering—quite pleasing effects.