Pitch Shifting

Scott Gravenhorst, Synthaholic chordman at ix.netcom.com
Mon Mar 18 03:35:51 CET 1996

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=============================== Original Message follows ======================

You wrote:
>   Date: Sun, 17 Mar 1996 12:38:04 -0800
>   From: chordman at ix.netcom.com (Scott Gravenhorst, Synthaholic)
>   Does anyone know of a circuit that will reliably add a constant
>   shift of the pitch of an input signal?  I know that it can be
>   done with multiple VCOs, run from the same CV with an offset for
>   one, but I was thinking more along the lines of a sideband type
>   of system.  Like taking a 6000 hz VCO output and somehow
>   combining it with a, say, 30 hz signal to produce a 6030 hz
>   signal.

>Don Tillman educated me with:

>(Nomenclature issue: "Pitch Shift" means changing the frequency of the
>input signal by a specified ratio, effectectively transposing by, say,
>a minor third.  "Frequency Shift" means changing the frequency by a
>specified number of Hz.)

Excellent.  Thanks for the nomenclature lesson.  I meant 'pitch
shifting'.  I take this to mean that the harmonic relationship between
the input signal and the output signal is the same, regardless of the
input frequency.  I am looking to provide a thickening of a VCO output.

The PLL circuit I have already built does a great job of producing
perfect fifths from a VCO supplied input.  I think the 33/32 circuit I
described might work, but it would be 'stuck' at 33/32.

>I'm not sure what you want exactly though...

Well, my brain is often in pain.  I'd like the harmonic relationship
between the input and output signals to remain constant.  BUT, I'd like
the relationship to be (knob) variable if possible.

So I'd say a ratio or 'pitch shifting' is what I want.  If it is
easiest to do with a square wave, no problem, I like square waves.

-- Scott G., Synthaholic

There is no 12 step program for synthaholics.  Thank your Superior Being.

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