Reel Rock and Scrub

When working with magnetic tape, audio engineers would locate edit points by grabbing the supply reel with their left hand and the take-up reel with their right hand, and moving the tape very slowly a short distance across the heads. In a music edit, they would listen for the attack portion of a beat. In a dialog or sound effects edit they would also listen for the attach portion or the leading edge of the sound. Since the reels are moved back and forth, this technique is known as “reel-rocking”.

When workstations first appeared, they often didn’t display audio waveforms, so visual editing wasn’t always an option. They also didn’t have reels, so the reel-rocking function was replaced by scrubbing. This was done either by turning a control wheel or moving a mouse, so that the audio would play slowly, just as if reels were being rocked.

Today, since most workstations now display waveforms, most edits can be made visually by observing the waveform to locate the attack of the sound. However, scrubbing can still be useful if the waveform display is low-level or doesn’t clearly show where the audio starts.