subtractive synthesis

A million years ago when I was very young I heard Wendy (but at that point in time Walter) Carlos' Switched On Bach. I think that it was the last movement of the 3rd Brandenburg Concerto that made my jaw drop and just sucked me into that world -- I desperately wanted a huge synthesizer that filled up rooms with equipment.

I only new the name of the synthesizer: Moog. I had no concept of "subtractive" or "analog" and so on. The first synth I ever got (much later) was the Roland Alpha Juno-2. Technically it's subtractive (it has digital oscillators and filters, etc, but has an analog sound). The only thing that made that hard was (1) there were no knobs -- all of the controls were buried inside and accessible only one parameter at a time; (2) I had no idea how synthesizers worked and consequently only made use of the presets occasionally making some modifications.

The thing is subtractive synthesis isn't hard to understand at all. And grasping it really makes it easier to understand what might happen when you start tweaking the parameters. (By the way this is absolutely not true of other types of synthesis like FM -- frequency modulation -- found on the Yamaha DX-7.) And these days software synths are cheap and easily available.

So what is subtractive synthesis? Here's my terse and possibly awkward definition: taking a basic sound (waveform) and filtering (i.e. subtracting out certain harmonics from) it to give a new (desired) sound. And if you're using a synth (software or otherwise) that's subtractive and want a little more info about it/them google the term and root around. Here are a couple of helpful sites:

DarkSonus
Yala
Wikipedia (this has a nice comparison with the human voice to make the mechanisms more easily understandable -- of course it's wikipedia and could change in a minute)

Here's a diagram I lifted from a KVR wiki which visually clarifies what's happening in this type of synthesis:



Of course in the end it's certainly not necessary to know how a synth works to use it effectively. But that knowledge can help you and aids in conceptualizing how sound works more generally.