Exploring FM synthesis with Operator
Ableton Live’s intuitive digital synth is ideal for exploration. Let’s build a typical FM bass…
Let’s explore frequency modulation synthesis using one of the most intuitive FM softsynths around: Ableton Live’s Operator. Don’t worry if you’re not a Live user, as these skills transfer to any FM synth. Using the default patch, we’ll stick with Osc 1’s Sine wave.
As we saw earlier, click the bottom-left section to expose the 11 preset algorithms at the top. Our first selected algorithm tells us that Osc D will modulate Osc C, C will modulate B, and B will modulate A. That means Osc A is the only audible oscillator.
Raise Osc B’s Level to-10dB: we now hear this second sine wave adding harmonics to Osc A’s pure sine. Next, in Osc B’s Envelope section, set its Sustain to -inf dB. Our shorter modulator signal is now only altering the front end of Osc A, giving us a nice, plucky FM bass.
Now select Osc C, give it an even tighter Envelope shape (see screenshot), then raise its Level. Osc C is now FMing Osc B, which is FMing Osc A – but this third, snappy modulator is only adding a tight transient click to the start of the note.
Make Osc C longer by extending its Envelope Decay. Our FM-like timbre is now really obvious. Try raising Osc C’s Coarse Frequency, and observe how the harmonic relationship changes. Now turn up Osc D’s Level and dial in the tight transient shape for a front-end ‘click’.
Finally, play with Osc B, C and D’s Levels, Coarse Frequency values and Envelope shapes to work out how these harmonic inter-relationships affect each other. Then, try switching oscillator waveforms to hear the effect on the final sound.