Carrier and modulator
One sine wave bends another.
Lesson 1 of 4
FM (frequency modulation) builds rich sounds from plain sine waves. Instead of filtering a bright wave, one sine wave wobbles the pitch of another so fast that you hear a new tone instead of a wobble. This panel plays Operator, TuttiDAW’s FM synth, which has four sine-wave operators named A to D.
Two operators
Turn up B Level, then click the operators in the diagram.
Each operator modulates the one below it; the ones on the output line are heard. Click an operator to see its own waveform and spectrum.
The operator you hear is the carrier (A here). The one bending it is the modulator (B). The diagram above the knobs shows that B sits on top of A: B modulates A, and A goes to the output.
B Level sets how hard B bends A. At zero, A is a pure sine. As you turn it up, more and more overtones appear and the sound gets brighter and more metallic. B Coarse sets B’s frequency as a multiple of the note.
Look inside each operator
Click B in the diagram to see the modulator on its own: always a plain sine. Click A: the carrier’s wave is bent out of shape, and its spectrum has grown a row of new partials around the note. Click Output to watch the sound itself again while it plays.