Analog Tape Speed Mechanics in Modern Digital DSP
In traditional analog recording studios—like the original Studio LOOS tape facility in The Hague—composers modified audio speed using the variable pitch controls (varispeed) on reel-to-reel tape machines (such as the Studer A80 or Revox B77). Increasing the tape motor speed shortened the duration while proportionally raising the pitch by the exact acoustic ratio of playback frequencies.
$$\Delta S = 12 imes \log_2( ext{Speed Ratio})$$
Musical semitone pitch transposition formula resulting from playback speed alteration
For example, speeding up an audio track to 1.25x transposes all musical notes up by exactly +3.86 semitones, creating the signature high-energy "Nightcore" sound. Conversely, slowing down to 0.82x transposes pitch down by -3.44 semitones, producing the classic nostalgic "Slowed + Reverb / Vaporwave" aesthetic.