Basic FM wires one modulator into one carrier. Real FM synths — the Yamaha DX7 chief among them — patch six operators into a fixed algorithm: a routing diagram of who modulates whom, and which operators reach the output as carriers. Pick an algorithm below and each operator's single slider does double duty: index (brightness) on a modulator, level (loudness) on a carrier — the same knob means something different depending on where the algorithm puts that operator. One algorithm also has feedback: an operator modulating its own frequency, which turns from a subtle edge into noise remarkably fast, so its slider is given far less headroom than a normal modulator's.
Shared brightness envelope — scales every active modulator (and feedback) index the same way, so the timbre opens on attack and settles, like the DX7's own index envelopes.
play with your keyboard (a s d f …) or click the keys