What Is PWM?

PWM stands for Pulse Width Modulation. It’s a technique where the shape of a pulse wave is modulated over time — making the waveform narrower or wider without changing its frequency.

To the ear, this creates movement and animation. It’s a classic way to add life to a static square wave, and it’s a signature sound in subtractive synths, string machines, and vintage polysynths.

How It Works

• A pulse wave is just a square wave with adjustable width — meaning how long it stays high vs low during each cycle.
• At 50%, it’s a classic square wave. But if you shift the pulse width, it becomes asymmetrical and takes on a different harmonic profile.
• By modulating that width with an LFO, envelope, or other CV source, you get a constantly shifting tone.

Why It Sounds So Good

Changing the pulse width affects the harmonic content of the waveform — subtly or dramatically. It’s like rotating the sound inside-out. This creates rich chorusing, wobble, and that “alive” feeling that analog synths are known for.

Common Use Cases

• Static PWM: Manually dial in a sweet spot — sounds thicker than a plain square wave.
• LFO into PWM: Classic animation. Great for pads, strings, and retro synth voices.
• Envelope into PWM: Add expression — widen or narrow the wave as part of the sound’s shape.

Pro Tips

• Don’t overdo modulation depth — subtle PWM often sounds more musical than extreme shifts.
• Try PWM on multiple detuned oscillators — you get a thick, swirling character that rivals chorus FX.
• Send PWM into a filter and modulate both for layered movement.

It’s a simple trick — but it makes a square wave come alive. PWM is one of those features that always feels worth it, whether you’re building fat basses, lush pads, or vintage leads.