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additive sythesis theoretical failures…

February 3, 2006 | 12:56 am

I have been working on a demo of additive synthesis for a class. I wanted to show the construction of tri, square, and sawtooth waves as mere sums of harmonics of sine waves. So i made a poly with a simple patch that mutes even harmonics for triangle and square, and adjusts the amplitudes (1/harm#^2 for tri, 1/harm# for sq. and saw) as necessary. The thing is, the oscilliscope doesn’t show a waveform that looks anything like it is supposed to (though the spectral content looks about right).
So I guess I need to make some sort of phase adjustment so the picture looks right…
How can I show the class that science is TRUE? :)

here’s my patches: http://www.yowstar.com/share/additive.zip

and, in the spirit of things, a Wendy Carlos instructional sample:

http://www.yowstar.com/share/sinesqorwhite.mp3

peter

on a related note, why aren’t the anti-aliased oscillators normalized from -1 to 1?


February 3, 2006 | 8:13 am

> I have been working on a demo of additive synthesis for a class. I wanted to show the construction of tri, square, and sawtooth waves as mere sums of harmonics of sine waves. So i made a poly with a simple patch that mutes even harmonics for triangle and square, and adjusts the amplitudes (1/harm#^2 for tri, 1/harm# for sq. and saw) as necessary. The thing is, the oscilliscope doesn’t show a waveform that looks anything like it is supposed to (though the spectral content looks about right).

Looks okay to me, mate – you just need to scale the waveform down
some.. Remember that unless you set the frequency high you’re only
getting a small fraction of the necessary partials.

> on a related note, why aren’t the anti-aliased oscillators normalized from -1 to 1?

It’s not possible to normalize them exactly because the peak value
can’t be predicted. Something seemed wrong about scaling to the same
amplitude as cycle~ and having the signal "clip" above 1, so I went
with the half amplitude instead… like phasor, I guess.

Ben


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