In the article "Boot Camp For Sound Programmers," (available here on the IAEKM website) you learned about the free SoundForum software synthesizer. Hopefully you’ve downloaded and installed it and spent a little time fiddling with the controls. (If you haven’t, you’ll find it under the SoundForum directory at Keyboard Online (Keyboardonline.com; a utility will guide you through the very simple installation process). In that article we set up a basic sound and looked at the signal path. In this article we’re going to spice up the basic sound by making some judicious adjustments in the settings.

Another Control Signal

In the "Boot Camp" article we looked at the envelope generator. This component makes no sound by itself, but it shapes how other parts of the instrument behave when you play the keyboard. The other important control feature in any synth is the LFO. An acronym coined by some bespectacled would-be Einstein, an LFO is nothing more momentous than a simple low-frequency oscillator. This is a breed of oscillator that generates very slow oscillations. These don’t actually become audible as part of the signal, acting instead as a kind of automated controller that modulates the pitch, tone color (essentially by rotating the filter cutoff knob, which you’ve already been introduced to), or volume of the signal.

Turn up the Amount knob in the LFO section. Now play with the Rate knob.

I take it that no further explanation is necessary. Note that the yellow "Osc P 1" button sends the LFO signal to the pitch of the first oscillator. And that’s a sound that certainly needs no further explanation.

Oscillator, filter, envelope, LFO - that’s it. Everything else is done with smoke and mirrors.

I can go on all day about how easy this is, but you won’t believe it until I show you. So here goes:

Now we’ll automate the knob (you won’t actually see the knob turn, but the sound will be the same as if it were turning) with the LFO.

Now you know exactly what it takes to go from the sound of a pinball machine to a pad fit for a film score — from zero to hero in just six steps. So you see, the things you have to do to achieve your sound design ambitions are not all that hard. This simplicity is what distinguishes simple synthesis (also known as "subtractive analog" synthesis) from fancier techniques like frequency modulation and additive synthesis.

You won’t find the pad we just created anywhere among your presets. You are, however, free to store the pad as a new snapshot:

Snapshots 2 to 8 show some simple unfiltered timbres. They come with an organ-like envelope, which means that pressing a key switches the tone on, and releasing it switches the tone off.

Give each of these snapshots a whirl. All are generated exclusively by means of Oscillator 1 settings, except for Basic Detune, whose beating (a slow swirling type of animation in the tone) is produced by a combination of two oscillators.

Of course this chart won’t let you create every sound under the sun. So what? It’s still a great way to get off to a good start. Think of it as your basic paintbrush technique — it will evolve until you develop a signature brushstroke of your very own.

In the following experiments, we’ll use some of the ideas in the table to turn a raw snapshot into a useful sound. This one was inspired by the legendary Roland TB-303. The only place you’ll find a more basic synthesizer is on a musical greeting card.

1. Select a snapshot: "2 Basic Square" or "3 Basic Saw". Set the Interval knob on Oscillator 1 to –24, because bottom end is what we want.

2. Hit the LP2 button in the Filter section. This selects a type of filter called a two-pole lowpass. (Don’t worry about what that means. If you’re curious, after lowering the filter cutoff, switch between LP4, LP2, and LP1 to hear the differences.)

3. Lower the Filter Cutoff to 80. Then crank the Resonance up to somewhere between 0.64 and 0.94. You should hear a more nasal sound as you turn it up. To get a better picture of what your waveform is doing, turn the Time knob under the Scope window to about the 9:00 position, and watch the scope as you add more filter resonance.

4. Now we’ll let the filter rip. Turn the Filter Env knob up to 100. Set the Filter Env knobs to the following values: A17, D38, S0, R39.

Sounds rather nifty, does it not? If you have a penchant for cute animation and want to see what the filter does to the waveform, crank the Decay knob on the Filter Envelope up up to 80, lower the Filter Cutoff to about 30, hold a note down, and keep your eye on the Scope.

And that brings us to this little nugget of wisdom: When you’re sculpting sounds, always bear in mind that the more overtones a lowpass filter saws off, the less angular or jagged the resultant waveform. Try choosing different filter modes with the buttons in the Filter section, play a long note, and check out what the waveform looks like.