Sound Synthesis

[Tony Hardie-Bick]

Oh Jeez. I must have thought this was a DSP list. Obviously I'm slowly 
going mad.

Tony Hardie-Bick wrote:
  > FM is by far the easiest. I say this, with my own particular bias
> against the negative aspects of digital synthesis (ie, all the stuff 
> that causes people to think digital is inferior to analogue). With FM, 
> you have a sine oscillator (use a lookup table of 1024 points with 
> linear interpolation, or 65K points without). Equip yourself with 
> "Musical Applications of Microprocessors" by Hal Chamberlin, and just 
> use the oscilltor output as a phase modulation source to other sine 
> oscs, and/or to itself.
> 
> If you go the subtractive route you're not gonna be ready to implement 
> an alias free square or sawtooth oscillator. That stuff is 
> counter-intuitive, and not fun until you've really hit on lots of other 
> tricks first. Heavy on the maths. Tough on the codability too.
> 
> Plenty of books will tell you to make a sawtooth waveform by simply 
> adding a number to a register (or integer variable) and let it 
> wraparound. Well, fine. That will give you aliasing. Same if you use a 
> conditional to get square and pulse width, unless you use a really high 
> sample rate (8x or 16x is beginning to be okay). The whole reason there 
> are still analogue synths in production, is because digital synths got a 
> bad name from these techniques. Personally, I believe digital is a 
> fantastic unlimited resource for acoustic aesthetics of unlimited 
> beauty, and have refused to compromise on such issues - so, up till now, 
> I have used FM in all the digital synths I built and programmed.
> 
> Filters are another area where digital has given itself a bit of a bad 
> name. Depends on what you're after. Many digital synths have simple, 
> well-implemented, high quality non-distorting filters. These are not 
> "warm" or crazy, or particularly characterful, but in the cold aesthetic 
> of the digital synth that somewhat prevails, this may in fact be an 
> enormous advantage (many excellent synth products fall in this category, 
> incl. all Virus models, Korg MS2000, all Roland's digital stuff). There 
> are only a couple of digital synths that seem to have captured some of 
> the roughness of analogue filters, and these are: Korg Legacy series 
> MS20, Elektron synths with SID emulation. Yamaha AN1X gets an honourable 
> mention. Many synths place a distortion stage (sigmoid LUT) after the 
> filter, which is the surest way to make a dull filter sound nasty, as 
> well as dull. The distortion belongs inside the iterated signal feedback 
> paths (ie, applied to a state variable) INSIDE the filter, not outside. 
> You need to choose your algorithm so that the overdrive is fed with an 
> appropriate signal. If you want to look at a no-compromise filter 
> written in C, you can grab this:
> 
> http://www.entity.net/DFM-1/downloads/dfm1.tar.gz
> 
> musicdsp.org has a load of algorithms, but you'd need to read a lot 
> before you'd get the big picture, and still some info seems missing from 
> there.
> 
> One great thing about FM, is you get variable spectra, without having to 
> do any filtering, and you can add that when you want to get into it.
> 
> Digital without cheese costs extra. Depends on what you're looking for. 
> Personally, I love analogue sounds, but would like to know *why* that 
> stuff sounds good, and put it down in code so I, and anybody else can 
> use it. FM is a great way to pursue this goal keeping the code intuitive 
> and therefore inline with one's goal of exploring the aesthetics of 
> musical programming.
> 
> Oh. Did I write all that?
> 
> Tony (HB)
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