Tape Speed Pitch Shift
Calculator
Results
- Speed ratio
- 1.350013
- Pitch shift (cents)
- 519.568601
- Pitch shift (semitones)
- 5.195686
Music and audio results
| Speed ratio | 1.350013 |
| Pitch shift (cents) | 519.568601 |
| Pitch shift (semitones) | 5.195686 |
formula-map diagram
- Speed ratio
- 1.350013
- Pitch shift (cents)
- 519.568601
- Pitch shift (semitones)
- 5.195686
Musical and acoustic relationship
Formula
cents = 1200 × log₂(playback speed ÷ original speed)= 1.350013500135
Note
This result is a simplified model: it applies the displayed standard formula to the values you entered, assuming twelve-tone equal temperament, a speed of sound of 343 m/s in dry air at 20 °C, an ideal free field with no reflections or air absorption, purely resistive speaker loads and Sabine's diffuse-field assumption. Real rooms, instruments, codecs and amplifiers depart from these idealisations, so measure with proper instruments for critical work.
More in Music and audio
See all →Frequently asked questions
How does changing tape playback speed shift pitch?+
Pitch shift in semitones equals 12 x log2(new speed/original speed), because speeding up or slowing down analog tape (or a turntable) proportionally speeds up or slows down every frequency in the recording together. Doubling the playback speed raises pitch by exactly one octave (12 semitones).
Why does speeding up tape also make it play faster, unlike modern digital pitch-shifting?+
Analog tape and turntables physically stretch or compress the recorded waveform in time as speed changes, so pitch and duration are locked together, you can't change one without the other. Digital time-stretching and pitch-shifting algorithms are what allow modern software to separate the two, something tape and vinyl mechanically cannot do.
Why do DJs and producers still care about this old tape math?+
Turntables (33⅓ vs 45 RPM), tape machines, and even the 'vari-speed' function on modern DAWs and samplers all follow this same speed-to-pitch relationship, so understanding it helps predict exactly how much a pitch fader or speed change will shift a track's key. It's also the basis of classic effects like slowing a sample down for a lo-fi or chopped-and-screwed sound.
How much does a small percentage speed change actually shift the pitch?+
A common turntable pitch fader range of ±8% translates to roughly ±1.3 semitones, since 12 x log2(1.08) ≈ 1.33. This is why DJs use pitch faders for beatmatching within a semitone or so, rather than for large deliberate key changes.
Does the direction of the speed change matter for the formula?+
Yes, speeding up (a ratio greater than 1) produces a positive semitone shift upward, while slowing down (a ratio less than 1) produces a negative shift downward, and the log2 function naturally handles both directions correctly, including the fact that halving speed drops pitch by exactly one octave.