FM and envelopes
Brightness that changes over every note.
Lesson 4 of 4
Every operator has its own envelope. On the carrier it shapes the volume, as usual. On a modulator it shapes how much FM there is, so the brightness changes during each note.
An FM electric piano
Move B Decay and B Sustain.
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.
Drag the squares on the envelope, or turn the knobs: they move together.
Here B’s envelope decays: each note starts bright and metallic, then mellows towards a pure sine. B Decay sets how fast, B Sustain how much brightness stays while the note is held. Watch the waveform on Output: it starts jagged and smooths out.
A fast decay on the modulator gives the bell-like attack of electric pianos and mallets; a slow attack gives brass that swells brighter. This is how classic FM keyboards made so many sounds from sine waves.