Morning good people,
I'm making steady progress on a simple polyphonic MIDI synth, and the post title says it all really. I have a single phasor driving a variety of oscillators (rect, saw etc), and am about the polyphonise (?) it. Would you put that phasor inside the clone object, where the shaping functions will go, or not? An 'outside' signal will of course go to all voices, and there may be phase issues with mutiple copies if I put it inside.

Kinda answered my own question there, but would love to hear your thoughts

PD-Pi

Thanks for chipping in. I should have mentioned a few things: this won't be a commercial or professional product, just for my own noodlings (I was looking at Behringer's recent line of HW synths and thought, why am I spending money, just build one in PD). So, the detail you mention isn't critical to me.

I could of course just make two different versions and see which one I like the sound of; plus, doing it that way will throw up any issues along the way.

Thanks again
Brendan

@PD-Pi Wait, if each clone instance is a voice, then they can't share a single phasor because then they'd all have to play the same pitch, which is not my understanding of a polyphonic synth.

yep! you're right, i'll keep chipping away at this, thanks

@jameslo said:

@PD-Pi Wait, if each clone instance is a voice, then they can't share a single phasor because then they'd all have to play the same pitch, which is not my understanding of a polyphonic synth.

the idea of using a central phasor is not that the frequency must remain the same all the time, rather you would derive sub-phasors from it or use forms of distortion - or clock multiplying - while everything can still be resynced from the master.

that is also how you can realize a naive hardsync oscillator among other things.

the master would be outside the clone patch of course.

@Obineg Interesting. Can you show me a patch that, say, generates all 12 equally tempered tones starting with middle C from 1 phasor?

Hi
I'm not sure what the PD equivelants are, but in Max I would have done this with rate~ on a central phasor. I think (it's been a while )

Brendan

@PD-Pi Just read the documentation for rate~...also interesting. I wonder how they do that?

You mean how it works internally? Probably a modulo function.

@PD-Pi Yeah, but the devil's in the details. I'd love to see a patch.

"The devil's in the details" and the particular detail is "equal tempered."

Can you show me a patch that, say, generates all 12 equally tempered tones starting with middle C from 1 phasor?

3:1 is not an equal tempered frequency ratio -- it's a justly tuned octave+fifth. The 12ET octave+fifth is 2.9966141537533 (approximately, since it's a fractional power of 2, thus irrational).

The [*~] --> [wrap~] approach will definitely have sync artifacts for non-integer ratios. Not sure what Max's [rate~] will do.

hjh

@ddw_music Yep, more reasons why it would be great to see a patch.

This morning I'm thinking that in the case of equal temperament, would sync between two oscillators even be meaningful? If the ratio between two pitches is a floating-point approximation of an irrational number, well gosh, that's as complicated as having no sync at all, isn't it?

@jameslo said:

Can you show me a patch that, say, generates all 12 equally tempered tones starting with middle C from 1 phasor?

You could do something like this ... phasor-sync.pd

Note sure if that's anywhere close to what's going on inside Max's [rate~], though.

@manuels That's clever, thanks! I especially like how you get the slope of the input phasor (compensating for that downward jump every cycle) and how you construct the output phasor. But I think there are two issues with it. Firstly, a sync will reset the phase of the output phasor at an arbitrary point unless the output phasor frequency is an exact multiple of the input frequency. Secondly, without sync, I think the output phasor may drift WRT the input phasor due to floating point roundoff error. Agree?

Backing out to look at the big picture again, i.e. Brendan's question, this means that it couldn't be used to make either a "hardsync" synthesizer (disclaimer: I don't really know what that is) or a "phasor~-synchronized system", assuming that both require a precise phase relationship between the input and output phasors and that the output phasor doesn't contain discontinuities. What do you think?

@jameslo I agree with both of your points. Except that I thought a hardsync oscillator would do exactly what you describe: reset the phase of the output phasor regardless of its current phase. So unless I'm mistaken here (which is very possible), my approach should be usable for that.

Wheter it can be used for a synchronized system with a central phasor I'm not so sure ... Maybe the mode (sync or non-sync) should depend on wheter the scaling factor is an integer or not? On the other hand: If it is an integer, the multiply-wrap method suggested by @PD-Pi is of course much simpler and probably more precise.

I just want to thank everyone for the detailed responses here, which has inadvertently but interestingly diverged into a slightly different topic. It makes interesting reading.

PD-Pi

@PD-Pi Oh sorry, I didn't mean to digress, I honestly thought this was relevant to your original question.

@jameslo Not derailed! Just expanded and extended