Oscillators: Essential Waveforms

Oscillators: Essential Waveforms

25 October, 2007 | 12.18PM

• Section: Music News Topics: Guide To Synthesis, Technology
• Written by: francispreve

Now that you have a handle on the signal flow of subtractive synthesizers, it’s time to dig into the specifics of the oscillator module.

To begin, let’s take a look at the most common waveforms you’ll find in an analog-style synth.

Each has its own distinct sound, so it’s important to understand their individual strengths. 

Sine

The sine wave is the “atom” of the sonic universe.

Consisting of a single harmonic – often the fundamental, or root pitch – the sine wave generates the simplest sound of all the waveforms, and therein lies its strength.

If you’re looking for that deep sub-bass that anchors many drum and bass tracks, start with a sine wave.

Similarly, you can use a sine wave is to add beef to any of the other waveforms by tuning it to the same pitch (or an octave lower for even more low-end bombast), then balancing the oscillator mix until it suits your purposes.

Alternately, you can use a high-pitched sine wave to add a specific type of shimmer to bell-like textures.

Sawtooth

At the opposite end of the waveform spectrum is the sawtooth wave.

Consisting of all integer harmonics, the sawtooth has an extremely bright and buzzy sound that makes it the Swiss Army knife of synth waveforms.

Used in conjunction with a moderate lowpass filter setting, sawtooth waves are great for subtle pad sounds.

Open the filter up to maximum and add a slightly detuned sawtooth to the second oscillator and you’re on your way to creating classic trance leads.

Lower the filter cutoff to about 30-40% and add some filter envelope modulation and you’ve got the essentials for a timeless bass sound.

Square

The square wave has become a bit trendy in dance music for the past several years.

Because of its Nintendo-esque hollow character, it lends itself to bright electro leads, glitchy embellishments and tech house bass lines.

The harmonic content of a square wave consists of only odd numbered harmonics, descending in volume in a linear manner.

That is, every successive odd harmonic is slightly quieter than the previous one.

Mixing square and sawtooth waves, especially in different octave ranges, can result in more complex harmonic combinations.

Alternately, you can use a square wave as the basis for emulated woodwind/reed sounds like flutes and clarinets.

Triangle

While its shape is quite different from that of a square wave, the triangle wave also contains only odd numbered harmonics.

The difference here is that these harmonics descend in volume in an exponential manner.

In plain English, this means that the triangle sounds like a more muted – or duller – square wave.

This makes it quite useful for supporting other waveforms without getting in the way, sort of like the sine wave but with additional harmonic character.

Pulse/Rectangle

The pulse wave, sometimes referred to as a rectangle, is a very flexible beastie.

Many synths have a pulse-width control for their square wave option, which is how this waveform is created.

In the case of a square wave, both sides of the cycle have 50% durations, hence the square shape.

If this duration is changed to 60/40, 30/70 and so forth, the harmonic structure shifts, giving the pulse wave a reedier character that’s quite useful in situations when a sawtooth is a bit too overbearing.

What’s more, when you use an LFO to modulate the pulse-width continuously, it serves to thicken the sound and is great for pad and lead sounds.

Noise

Noise generators are often found in addition to the oscillators on a synth, as well as a waveform option.

White noise is created by generating every possible frequency at the same volume.

Some synths include a “color” control to vary the frequency content somewhat, creating three basic types of noise: white, pink and blue.

Pink noise has slightly emphasized lower frequencies, whereas blue noise is slightly tilted toward the highs.

In its raw form, white noise sounds like old school television static, but if you apply a filter to it, you can shape the sound to create everything from nature sounds to vintage analog percussion effects.

Ocean waves and wind sounds are emulated by applying a filter to a noise source.

In modern club tracks, one of the most common uses for noise is to generate those giant whooshes that come at the end of a long breakdown, bringing the track to its peak.

Hybrid and Digital Waveforms

Finally, many softsynths (notably, Reason’s Subtractor synth) include an array of additional digital waveforms that have more exotic harmonic content.

Some of these waves have vocal qualities, others have bell qualities, and so on.

These waves are excellent for creating more metallic, digital sounds, but often don’t have the same perceived “warmth” that the classic waves have.

That’s not to say they’re bad; it’s all a matter of your production objectives.

[PPG Wave, right image: The PPG Wave was the first mass-produced synth to rely on digitally generated wavetables for its oscillators. The originals are collector’s items, but fortunately for us, Waldorf has released an affordable softsynth replica.]

Speaking of Reason, I strongly urge readers who do not already own a sequencer or digital audio workstation software to head over to www.propellerheads.se and download the demo version of Reason.

Doing so will allow you to follow along with these lessons, testing and experimenting as you go.

In the next lesson, we’ll talk about mixing multiple oscillators.

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