FM velocity sensitivity routes key-strike force to modulator amplitude, creating touch-sensitive brightness

On the DX7 and related FM synthesizers, each operator has a velocity sensitivity parameter. When set on the modulator, harder key strikes increase the modulator’s output level, producing a brighter sound; softer strikes reduce modulation and yield a duller tone. This creates the same expressive characteristic as velocity-sensitive filter cutoff on an analog synthesizer — hitting harder opens up the sound. When set on the carrier, velocity controls loudness only. Setting velocity on both modulator and carrier simultaneously gives independent control of brightness and volume relative to touch, enabling highly expressive programming.

Examples

FM Demo 1-B: Op. 2 is velocity sensitive. Playing hard sounds like FM Demo 1-A (bright, filter-open). Playing softly reduces modulation to near zero, producing a muted sine-like tone.

Assessment

Distinguish between setting velocity sensitivity on the modulator versus the carrier in a two-operator FM patch. What parameter does each control, and how does the player experience each difference?