Record Scratch

How it's made

Source

a hand pushing and pulling a vinyl record under a stylus. The groove carries a harmonic, music-like signal (a detuned saw pair plus a square an octave down); the platter speed scales its pitch and its level, and a reversed pass sounds the same as a forward one because only the speed magnitude is heard.

Surface

stylus and dust give gritty noise (band-passed white, 0.8–5 kHz) whose centre and level follow the speed, plus sparse crackle ticks; the grit gets louder when the groove is moving fast.

Envelope

speed is a signed breakpoint curve, forward 1.7x, back 1.9x, forward 2.2x, back 1.4x, forward 1.0x, then a hard hand stop in about 25 ms. The direction changes pass through zero speed, which gives the pitch dips and level notches of a real scratch; a 4 ms fade closes the stop without a click.

Tone

a low-pass follows the speed (slow = dark and dull, fast = bright), so the spectrum opens and closes with every stroke instead of only the pitch moving.

Variation

`rng` jitters stroke peaks and timing by a few percent and the noise and crackle streams; `pace` stretches the strokes, `grit` the surface noise, `pitch` the record content, `stop` the final brake.

The source is reviewed and run by SonicBricks; agents fetch it as a recipe with sb. It is not published on this page.