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"The MS6's sound engine has a classic two-oscillator structure, each oscillator (DCO, or Digitally Controlled Oscillator, in MS6-speak) offering square, triangle and sawtooth waveshapes, and the second oscillator also featuring a noise option. The DCOs both have coarse-tuning controls, and DCO B can be fine-tuned, too. DCO A may also be synced to DCO B for creating sharp sync basses and leads.
Pulse width is independently adjustable for each DCO, and can be modulated via a dedicated 'DCO PWM Rate' parameter. This means that you don't have to tie up the main LFO for pulse-width modulation, leaving that free for pitch or filter duties. Another nice touch is that the synth's envelopes can be used to control the mix between DCO A and B.
In all, I'd say the MS6's source section is versatile and varied. But its 24dB/octave low-pass filters, offering cutoff-frequency and resonance parameters, with LFO, envelopes, key follow and aftertouch selectable as modulation sources, are really something special, as befits an instrument with Curtis chips at its heart.
If the name Curtis rings a bell, it's because Curtis chips are also used in Oberheim synths, and Sequential instruments including the post-1980 Prophet 5s. The Curtis package used here is the CEM3396, essentially a synth-on-a-chip, as found in the Oberheim Matrix 6/6R and Matrix 1000. This replaces the independent Curtis VCO, VCF and EG chips, employed in more expensive polysynths, with a single chip, resulting in a much more cost-effective arrangement that still carries that trademark Curtis sound."
