BTW, I have a noob question @Ligia @JimHowell1970. If a VCO has 1 Sub-Osc (-1 Oct) output; should I have at least 2 filter, 2 VCA and 4 EG minimum for that particular Oscillator?
-- Hikove
Nope. Well, actually, you CAN, but it's overkill. One of the most respected monosynths of all time (the Roland SH-101 and, by extension, the MC-202) also has a single VCO + a suboscillator, and the synth simply mixes those two together pre-VCF. However, it IS worthwhile to have a VCA available for the suboscillator since that will allow you to add/remove that part of the oscillator composite signal like you would do with any other source. So, say, you can have a hard attack on the basic output, but with a slower attack sent to the suboscillator's VCA, this would then "fade up into" the main VCO sound.