If your oscillators have a linear response, yes you could do that.

And sorry, it’s not a new idea. I can make patches on my synth that allow me to play full chords with a key press.

I don’t know if the trio of oscillators forming a chord is going to satisfy you. For a really great oscillator sound, having multiple oscillators playing the same note helps a lot. Usually the oscillators are all a little bit off in tuning and in phasing, which really fattens up the sound.

The other thing that helps is filtering. When you have a square wave you’re getting the base note with all the harmonics. Filtering it will take away some harmonics and give you a more interesting sound. This is known as subtractive synthesis. Another thing that helps with oscillators is called pulse width modulation. In a usual square wave we see that the up and down time are both the same. With pulse width modulation you can make the up be longer or shorter than the down, to fatten or thicken the sound respectively.

Well OK. . .

Imagine you have an oscillator with a voltage input.

At 1v you have C3, At 2v you have C4, at 3v you have C5 and so on. That works out very well, because you know when you increase voltage one volt you go up an octave.

So imagine you have three parallel oscillators tuned to the root, the 3rd, and the 5th (the steps that make up a major chord.)

You have it set up so that oscillator 1 gets 1v for C, oscillator 2 gets something like 1.4 volts for E, and something like 1.6 volts for G. You increase everything by one volt, and all the notes remain the same.

However, if you build an oscillator that doesn’t have a linear response- say that instead

C2 = 1v
C3 = 1.5v
C4= 2.5v
c5 = 5v

and so on and so forth. . . this means that the voltage change to get a certain musical interval is never constant. If the voltage change to get a certain interval is different for every voltage, when you increase the voltage to raise your C an octave, since your E and G are higher notes, they’ll go higher than an octave since the voltage increase per octave goes higher with each note. So then although the chord will be in tune on one setting, it would be way out of tune on another.

Now that I think of it more, I don’t think what you want to do will work that way.

There are some ideas flowing through my head right now of what would work best, but you should really post this at DIYstompboxes.

I’m thinking you either want to add a separate voltage to each oscillator, or you want to tweak each oscillator’s tuning via the oscillators circuit.

That’d work too.