AudioScope
Why Does Faster Playback Raise Pitch?
Listen for two changes when the same recording plays faster. The pitch rises and the pulses move closer together.
What happens at 1.35× speed?
Playing a 33⅓ RPM record at 45 RPM multiplies both its pitch frequencies and its pulse rate by 1.35. In this original listening test, the 440 Hz tone becomes 594 Hz. The same passage takes about 74% of its original time.
To raise the pitch by an octave through speed alone, double the playback rate. Digital time-stretching can change the duration while preserving the pitch.