You are here

Software Synthesis; Hybrid Software

Apple Notes By Martin Russ
Published June 1998

Software Synthesis; Hybrid Software

Having whetted his appetite for MacOS‑based software synthesis last issue, this month Martin Russ takes a closer look...

Last month, I mentioned that it might soon be worth looking at software synthesis a little more closely, and there's at least one very interesting new package on the way. But in the meantime, let's consider what programs are available now, and how they work.


A simple and rather less simple example from the freeware Syd 1.0.6.A simple and rather less simple example from the freeware Syd 1.0.6.

The obvious place to start is with the software synths I'll call the 'Literals' — programs that give you an on‑screen representation of analogue synthesizer modules, complete with knobs, switches and patch cords, such as Digidesign's TurboSynth, and the BeOS‑based Audio Elements. With these programs, what you see is exactly what you get, and in order to produce decent sounds you need to understand a few basics of analogue synthesizer programming. If you haven't been reading Paul Wiffen's Synth School series, here are a few condensed tips:

  • Sine waves are so boring that you have to add vibrato to them to make them even slightly usable.
  • Square waves are so dull and hollow that you need to liven them up with some sort of modulation, such as Pulse Width Modulation (PWM) — normally a Low Frequency Oscillator (LFO). The same LFO that you used for the sine wave vibrato will do. Try an envelope as an alternative PWM mod source .
  • Sawtooth waves tend to be very bright — take two and detune them to get a glorious chorus effect. This also works with square waves, but note that using PWM as well might be considered overkill.
  • Filters should always be swept, preferably with an envelope, though an LFO will do for tremolo‑like effects. Long decay times are always preferable to static sustain segments in envelopes. Turning the resonance to just below self‑oscillation is also recommended.


Software Synthesis; Hybrid Software

'Hybrid' software synths such as Syd (see below) combine tasty on‑screen graphics with hidden complexity and detail. There's often the same patching together of blocks, but the capabilities of these blocks may well surpass that of analogue synthesizer equivalents. There's more power, but the blocks tend to employ mathematical functions and formulae which can make them awkward to use.
The key to understanding this type of software synthesis is to carefully examine some example patches — though it doesn't hurt to have a tame mathematician on call! Fortunately the maths involved tend to be quite straightforward once you get the hang of it.

For example, in Jim Bumgardner's Syd (the software synthesizer formerly known as SoftSynth) you can work with a simple oscillator that produces the classic sine, square, sawtooth type of waveshapes, or you can 'grow your own' by describing the shape using a mathematical formula. Non‑mathematicians beware: you have to remember to multiply the time by 2*pi to produce a whole cycle's‑worth of audio, hence its appearance in all of the examples below:

sin(t*2*pi) produces a sine wave!
tan(t*2*pi) gives a nasty pulse‑like waveform
mandel(t*2*pi,g*0.1+0.5) uses the Mandelbrot set to illustrate gross quantisation noise on a decaying envelope! (g is global time here, whereas t is time within one cycle of the waveform).
turb(t/(n+.01),g*3)*sin(t*2*pi) uses fractal noise to give a very nice synthetic timbre which sounds like it has had a resonant low‑pass filter sweep applied to it. n is the time since the note started.

As you can probably see, you need some idea of what you're doing when you fiddle with these formulae, but there's still plenty of scope for just plugging in numbers and functions and seeing what comes out. Which is how I found this:
dragon(t*1.5,g*0.01+0.5,i*0.010,g*0.01) — a complex little rasp of a sound, far more complex than you would expect from a simple oscillator calculating values that end up in an AIFF file. I like Syd, and the two of us may well collaborate on an album in the near future.


If you're comfortable with more complex mathematics — perhaps you do Digital Signal Processor (DSP) programming in your spare time — then what I call 'Mathematicals', potentially the most challenging software synthesizer programs, may be for you. Out Of Phase is an example I've mentioned before, but CSound is another example of software with a steep learning curve to ascend. With Mathematicals there's normally a programming language to learn, and you may need to generate waveforms, process them with envelopes and filters, and even write the score to play them before you hear anything. Reading the manual is very important here, as is lots of experimentation. The advantage of these programs is that they place few limits on the sounds that you can produce — except those imposed by your imagination and programming skills.

This is why the MPEG4 multimedia standard gurus have specified exactly this type of 'DIY audio programming' for sound generation in the forthcoming audio/video/multimedia coding format. SAOL — the Structured Audio Orchestra Language (an example of an acronym whose meaning doesn't become clearer when you know what the letters stand for!) — is exactly this type of 'grow your own orchestra' programming tool with very few inherent limits: physical modelling and wavetable, FM, additive, and subtractive synthesis are all possible. Playing around with a serious maths‑based software synthesizer now could well provide you with the coding skills that will be required in the next generation of multimedia applications. What's more, it's also very unlikely that a hardware synthesizer is ever going to provide anything like this depth of user programmability.

Apple News In Brief


Given the carefully designed 'platinum' look of MacOS8 and 8.1, Kagi's shareware website registration statistics are interesting. For the last year, one piece of shareware has consistently been in either first or second place. That software, Kaleidoscope, is a very powerful way of customising the appearance of your MacOS: screen colours, scroll bars, go‑away boxes, and the like can all be extensively tweaked — and there are loads of of pre‑prepared colour schemes for you to try. There are even System 8 look‑alikes for System 7 users! Nevertheless, as with all such 'fun, but musically unrelated' add‑ons, this is definitely one to avoid adding to the Mac you use for music, despite its seriously high cool rating. The next MacOS, codenamed Allegro, may well incorporate 'themes' to allow exactly this type of in‑depth customisation, so wait for that if you feel you need this facility.


Hands up all those who thought that the eMate — Apple's new personal mobile computer aimed at the education market — was such a wonderful idea that it was stupid to restrict it just to schoolkids. Keep those hands up when I tell you about the new low‑cost all‑in‑one design (computer plus built‑in monitor) G3 machines that aren't quite the sub‑$1,000 boxes promised, but are certainly a stab in the right direction. So what's the problem? You got it: these machines are solely for the educational market and then only in the US. However, if past events are anything to go by (the eMate was offered to Sunday Times readers as a special offer) then this latest 'restricted audience' Mac may eventually turn up over here in one guise or another.

Tip Of The Month: Mouse‑Cleaning

Almost without exception, I find that I can make a significant improvement to the performance of just about every hard‑working Mac (and PC) computer that I look at. There's no magic involved, just a thorough cleaning of the mouse (or in sad cases of neglect that would make Rolf Harris weep, I just quietly put it to sleep and get a complete replacement).

There's a Mac program which actually measures how many miles your mouse has travelled, which strikes me as one of life's less significant statistics. Nevertheless, the result of all these miles of travel combined with the effects of sweaty hands, grime and dust is that the rollers inside your mouse become encrusted with a black/grey gunge that makes cursor or pointer movement characteristically jerky — in extreme cases it may stop altogether at times. There is, however, a simple cure — all you need is a fingernail and a little breath, although you can spend a small fortune on gadgets designed to accomplish something very similar (a small fortune which might be better spent on a brand new mouse).

Here's what to do: first off, you open the mouse by twisting the circular plate on the underside. (Usually it comes off anti‑clockwise.) After removing this plate, turning the mouse upside‑down so that the ball drops out — this should expose its innards. If there's no ball, then you may have an optical mouse (a rare beast!), and you shouldn't need to clean anything other than the special reflective mouse mat. If the ball seems rather lightweight, then you may have one of the dysfunctional early '90s mice which had a ball that was simply too light to grip properly — in which case you should just buy another.

Inside, you will probably now see three little rollers. Two are at right angles to each other, and may well be made of shiny black plastic, whilst the third roller is diagonally opposite them and is often made of white nylon. All three rollers will probably be encrusted with the dreaded gunge, which can be easily removed with the fingernail of your index finger — just drag it diagonally across the surface of the rollers several times until the whole of the surface has passed under your fingertip, and all the gunge is gone. Blowing into the mouse at this point should remove the fragments of grease, grime, dust and fluff, and you can proceed to the next roller.

In my experience, using Q‑Tips and the isopropyl alcohol you might use to clean tape heads does not work — what's more it can leave sticky deposits on the rollers, as well as fluff from the Q‑tips. Contrary to what you might imagine, the balls themselves rarely seem to need cleaning. Once you've cleaned the rollers, replacing the ball and twisting the plate back should restore your little desk rodent to full health and normal operation.