[sdiy] pitch to voltage

[harry bissell]

One problem of the added harmonic method
is that some very real sources (my guitar
for instance) have non-harmonic overtones.

The stiffness of the strings makes the overtone
series sharp... so adding the "right" overtones
might be impossible.

I think the result would lead to intolerable
IM disortion.

Sort of the same problem as using a multiplier to
get a 2X frequency shifter... it only works on a 
pure sine wave.

But hey I hope I'm wrong. I want a perfect shifter
as well....

H^) harry



--- Dave Krooshof <krooshof at xs4all.nl> wrote:
> >on 11/4/01 4:23 PM,  at krooshof at xs4all.nl wrote:
> >
> >> Then we waveshape 150, 250, 350 etc. into it. A
> bright 50 Hz is heard.
> >> Any ideas on how to do this in (analogue?)
> hardware?
> 
> >If you put a divide by 1.5 circuit in the feedback
> loop of a PLL, you can
> >get multiplication by 1.5 so 100*1.5=150, and so on
> with the others.
> OK. But I'm a little pessimistic. This is how I see
> the route:
> First I have to split up the sound in seperate
> overtones. Then the deviding
> is not a problem. But I'd do the splitting in an
> Fourier analysis, and having
> that it's easy to shift to any pitch. Even then, I'm
> pessimisic about
> being able to distinguish between the seperate
> overtones. After FFT I'd
> just shift the whole lot as one thing.
> 
> >Also, if you use a phase shift type of delay,
> >(which isn't very practical),
> Just my luck.
> 
> >you'll get a frequency dependent amount of delay.
> Joy!
> 
> >I'm not sure those halfway numbers are correct
> (150,250)
> We are discussing a 100Hz input, and we want 50
> output.
> The 'halfways' are correct as they are part of the
> list of 50Hz overtones,
> which is 100, 150, 200, 250, 300 Hz...
> We already have 100, 200, and 300 from the input.
> Then we do not realy
> need the 50Hz, as our ear/brain will derive that
> pitch in pattern recognition.
> To complete the pattern for 50 Hz, adding generated
> new overtones at
> the halfway numbers will do.
> So my idea is radical in that respect that I forget
> about the suboctave
> itself, but only trick the ear in believing it was
> in the air.
> 
> I'm hoping that just delaying would be a 1.5 or 0.5
> multiplication stand in.
> 
> 
> 
> 


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