An Introduction To FM Synthesis

Ableton Live Operator

To show how other FM synths work in similar ways, let’s begin by recreating this patch in Ableton Live’s Operator synth. Operator might not look much like FM8, but under the hood it has a similar architecture. Rather than a modulation matrix, Operator has a selection of preset routings, much like the Yamaha DX7. In the master panel at the bottom right-hand corner of the interface you’ll see four coloured blocks:

This represents how the synth’s operators are routed. In this case the yellow Operator A is at the bottom, which means its the only one that’s voiced. B modulates A, C modulates B, and D modulates C. Turn Operator B’s level up to 0.0dB and you’ll hear mode harmonics are introduced into Operator A’s output:

B is acting as the modulator, A as the carrier. Drag down on the square near the centre of the volume envelope on the right to adjust the envelope, making B’s level drop over time as a note’s held down:

This gives us that filter-style movement we created before.

Set operator B’s Coarse tuning to 2, and we’ve made the same raw deep house bass as we had with FM8. Turn B’s Level down to -12dB or so to smooth the effect out:

Logic EFM1

Next, we’ll see how Logic’s EFM1 takes an even simpler approach to FM synthesis. The instrument is based around just two operators – a dedicated modulator and a dedicated carrier – and its default patch is much like the deep house bass we’ve already encountered. The modulation amount is controlled with the FM Depth knob and the ADSR envelope to its left:

By turning up the FM Depth and the ADSR’s Sustain level we can devolve the sound to the harsh, harmonically rich sound we had in FM8 and Operator before we tweaked their envelopes and modulation levels:

Finally, the modulator’s Harmonic knob controls its pitch, and like FM8’s Ratio and Operator’s Coarse parameters affect the timbre of the sound.

The carrier and modulator relationship we’ve explored in this walkthough is simple, but once you’ve understood it you’re well on your way to grasping the potential of FM synthesis. No matter which FM synth you have access to, understanding these basic principles is the key to unlocking the power of FM synthesis. By experimenting with different operator ratios, envelope shapes and modulation routings, it’s possible to create much more complex, exciting sounds. We’ll be returning to FM synthesis soon to explore some more complex sounds in greater depth. Until then, don’t be scared to jump in and have a go at FM synthesis – it’s not as scary as some people might make out!