Pushing Partials Around
2000-03-22 by Tkacs, Ken
Really? I find that very strange. I've *always* approached synthesis with the harmonic spectrum in mind. The waveform is the *result* of the sound's harmonic content. When you're creating sounds, isn't it better to think in terms of the harmonic alterations rather than the shape of the wave? When applying a lowpass filter, for instance, I imagine it as something like a window-shade closing down on the spectrum, not as rounding off the peaks of a sharp waveform. The ear hears the spectrum, not the oscilloscope image. Also, additive synthesis and Fourier analysis predate digital by a pretty good margin. These were terms that we used to discuss in the old analog days long before the first digital synthesizers hit the market. While I agree that additive synthesis is probably easier to implement in digital, I don't think it's at odds with analog at all. That's why we use more than one VCO! I agree that waveform manipulation is easier in analog, and I think that the discussions of waveform shapers, folders, and multipliers can be very fruitful. But as a generalization, they still only affect the amplitudes of the existing harmonics (I usually use the term "partials" because it was beaten into me that the Fundamental is not a harmonic, so when you want to refer to *all* of the Fourier components, including the fundamental, you need to use 'partial' rather than 'harmonic.' Although in recent years it seems that the misuse of the terminology is getting ingrained into the language, the same way that "font" is used to mean "typeface" when that's not proper either). Know what I mean though? After the fundamental, the harmonics in simple waveforms are specified as period-times-1/2 (octave, or first harmonic), times-1/3 (octave-fifth, or second harmonic), times-1/4 (two octaves, or third harmonic, etc.). You can filter this, waveshape it, and so on but you still aren't changing these relationships unless you run the signal through a ring modulator. The fact that these relationships are 'set in stone' while so many other aspects of the sound are open to us for manipulation ... *bugs* me :) . The reason this kinda thing keeps me up at night is because I'm interested in microtonal music. Our musical scale closely parallels the harmonic series of simple waveforms like we've been talking about (at least until you get up in the range where the compromises of equal temperament cause a divergence). When you look at the unusual scales of other cultures, like the music of the gamelan, they aren't just playing weird tunings with Western instruments---their instruments produce tones with harmonics that echo and fall in line with their scales, just as ours does. We have instruments that produce "simple waveforms" (please allow me that ridiculous statement) that work with our equal tempered scale, and they have instruments that have complex tones and scales to match them. I find this whole thing very interesting. I'd love to play with those relationships. Sure, digital's always an option, but I want to do it with patchcords and knobs! Typing on a keyboard to specify harmonics is for the birds.
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-----Original Message----- From: jwbarlow@... [mailto:jwbarlow@...] Sent: Tuesday, 21 March, 2000 10:40 PM To: motm@onelist.com Subject: Re: [motm] Modules for Pushing Partials Around I think viewing waveforms as a composite of harmonics lends itself much more to digital (through Fourier analysis). It seems that when you view a sound as a waveform you are more "in tune" with the basic ""philosophy"" of "analog synthesis." As such, I think a more easily solvable engineering problem would involve manipulating the waveform in unconventional ways.