FM sound design

How to Make Nasty FM in Serum

By Psiger · Updated July 2026

Watch the full breakdown

The nasty, aggressive FM sounds that cut through a full-on track come from frequency modulation: one oscillator modulating another to generate dense, gritty harmonics. Get the setup right and you have a growl that sits perfectly in psytrance.

In the video Psiger builds the sound in Serum and shows how automation makes it come alive. Here are the stages.

Key takeaways
  • Nasty FM comes from one oscillator modulating the frequency of another.
  • The FM amount controls how much grit and harmonic density you get.
  • The ratio between the oscillators decides whether it sounds musical or dissonant.
  • Push the FM amount for grit and tune the ratio to keep it usable.
  • Automate the FM amount and filter so the sound morphs from clean to filthy and stays alive.

The nasty FM demo

▶ Play from 0:00
The nasty FM demo — screenshot from the video

The target is an aggressive, gritty FM growl. Hearing it first shows what you are building toward: harmonically dense, biting, and full of character, the kind of sound that cuts through a busy mix.

It all comes from FM synthesis, so the setup matters more than any effect.

The FM synthesis setup

▶ Play from 0:49
The FM synthesis setup — screenshot from the video

Set one oscillator to modulate the frequency of another. The amount of FM controls how much grit and harmonic density you get, and the ratio between the two oscillators decides whether the result is musical or dissonant. This is where the nasty character is created.

Push the FM amount for grit, and tune the ratio so it stays usable.

Automation to bring it alive

▶ Play from 8:22
Automation to bring it alive — screenshot from the video

A static FM sound gets old fast. Automate the FM amount and filter over time so the sound morphs from clean to filthy across a section. That movement is what makes the FM feel alive and lets it build energy rather than sitting flat.

Automation turns a good FM patch into a dynamic one that evolves with the track.

Common questions

Psytrance production FAQ

How do I make an aggressive FM sound in Serum?

Set one oscillator to modulate the frequency of another. The FM amount controls how much grit and harmonic density you get, and the ratio between the oscillators decides whether the result is musical or dissonant. Push the FM amount for aggression, tune the ratio so it stays usable, then automate it for movement.

Why does my FM sound harsh or out of tune?

Usually the ratio between the modulator and carrier is off. FM ratios produce different harmonic relationships, and some sound dissonant or clangy. Adjust the ratio until the harmonics sit musically, then use the FM amount to dial in as much grit as you want. The ratio is the key to keeping aggressive FM in tune.

How do I stop an FM sound from sounding static?

Automate it. A fixed FM amount gets old quickly, so automate the FM depth and filter over time so the sound morphs from clean to filthy across a section. That movement makes the FM feel alive and lets it build energy with the track, rather than sitting as one unchanging growl.