Planning the synth

I want to build a synthesiser. There, I said it. After years lusting after and admiring Yamaha's mid-late 70s analogue beasts such as the GX-1 and CS-80, I've decided to build something inspired by those same machines in both aesthetic and sound.

Probably the most notable thing about both the GX-1 and CS-80 is that they are polysynths. Mine will not be, for the simple fact that polyphony is very tricky to implement in synthesisers with as complicated a voice structure as the Yamaha models. Here's a list of features/specifications that I have in mind. These are all however subject to change based on further research.

• Monophonic
• 61-note keyboard (salvaged)
• Two independent voices with global modifiers (as in the CS-80)
• 1 On/Off Pulse wave with independent PWM per voice
• 1 On/Off Saw wave per voice
• 1 Noise source with level slider per voice
• 2 12 dB/oct resonant filters in HPF -> LPF configuration per voice
• 1 Il Al A D R filter envelope per voice
• 1 ADSR VCA envelope per voice
• Independent voice octave selectors
• Voice 2 detune lever
• Global brightness (vcf cutoff) and resonance levers
• Global keyboard scaling levers for brightness and volume
• Global sustain slider (increases vcf and vca release time on both voices)
• Sub-oscillator with selectable sine, ramp up/down, square and noise waves, affecting pitch, vcf, vca.
• Three presets per voice, selected by panel buttons and stored on passive resistor network cartridges (GX-1 style) that can be swapped and changed
• [possible] CS-80 style ring-mod section with Attack, Decay, Depth, Speed, Modulation
• [possible] Switchable reset/continue envelope retrigger response
• [possible] monophonic aftertouch

That's the idea so far, more snippets to come.