Monday, February 8, 2010

Synthesis Made Simple: Part 3 - Oscillators - Combination Style






















So, last time I introduced you to the OSCILLATOR, the starting point for just about any synth sound you’re likely to program. In listening to the “classic” basic waveforms most common to analog synths, you probably noticed that they sounded pretty thin – almost like a weedy little organ. So how do you get thicker, more complex sounds? (I honestly didn't mean for that last sentence to sound like it came from a "male enhancement" ad...)


Luckily, most synths are equipped with more than one oscillator per voice (2-3 oscillators is about average). What this means is that we can detune the pitch of one oscillator against the other(s) for thicker, fatter timbres. Usually oscillator tuning is altered with three different controls of varying coarseness: OCTAVE, SEMI, AND FINE.


Remember what I said about manufacturers liking to give different names to the same things? The same applies here. On many older synths, instead of seeing an OCTAVE control, you’ll see strange markings for 32’, 16’, 8’, 4’, and 2’. This is a holdover from the days of pipe organs where the length of the pipe determined the pitch of the note. The longer the ‘footage’, the lower the note. No matter how it is marked, however, all octave controls let you move the pitch of the oscillator up or down in increments of 12 semitones (aka an octave).


That’s all well and good, but what if I want to tune the oscillator by a smaller amount of semitones? That’s where the SEMI (sometimes called COARSE) control comes in. It allows you to tune an oscillator up or down a semitone (aka a note) at a time. Why would you want to do this? By tuning a couple of oscillators apart by the correct amount of semi-tones you can have a sound where, just by pressing one note, it plays an interval like a perfect fifth, or, if you have enough oscillators, even full blown chords. This technique is used a lot in techno and house music in particular.


These controls are great for ‘broad brush’ pitch adjustments, but where things really start to get interesting is with the FINE control (sometimes called CENTS or DETUNE). This allows you to tune an oscillator in increments of a “cent”, or 1/100th of a semitone. This is where you can really fatten up your sounds, and different amounts of this control can yield everything from a pleasant chorusing effect, to ultra detuned trance lead effects, all the way to very dissonant sounds. Some synths limit the range of detuning to what is most likely to be musically useful, but well-featured synths will let you use the whole range in between notes.


Some synths will also feature something called a SUBOSCILLATOR. A suboscillator is an additional, very bare-bones oscillator designed to simply play an octave or two below the main oscillator(s). This is almost always a very simple waveform like a sine or triangle. So what is the purpose of this? Aside from the fact that it definitely thickens your sound instantly, it's a great way to give bass sounds some extra low end 'oomph'.


Of course, if you have more than one oscillator, you need some way to mix and set the balance between them.  That's where the MIXER (sometimes called AMP ) section comes in.  This allows you to set a volume level for each oscillator until the balance is where you want it.  If your synth is stereo, you're likely to find a PAN control here too to set the position of your sound or oscillator in the stereo field.


These controls can be set in any combination you can imagine, already opening up all kinds of sonic possibilities, but when you consider that each oscillator can also be playing back a different waveform, you can see the potential open up even more. This is great enough with even a basic selection of ‘classic’ waveforms, but if you’re working on a synth that offers dozens or even hundreds of different waveforms, you can begin to see how limitless the range of sounds you can get out of a synth can be. And we haven’t even got around to filters or modulation yet!


Many synths offer additional ways of letting the different oscillators interact with one another such as OSCILLATOR FM, RING MODULATION or HARD SYNC, but that’s a bit more advanced than I’m looking to get here. Suffice it to say, these techniques add still more options for shaping your sound once you’ve mastered the basics.

Next time we’ll discuss a great tool for making non-pitched sounds, the NOISE GENERATOR.

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