Tape Speed Pitch Calculator
On an analog tape recorder, pitch and speed are directly proportional: faster tape speed raises pitch and slower tape speed lowers it. This relationship is described by the logarithmic formula: pitch shift (semitones) = 12 * log2(speed ratio). The same relationship applies to digital varispeed, time-stretch algorithms, and any process that scales playback rate. This calculator converts between speed ratio and pitch shift in both directions. Enter a speed ratio to see the pitch shift, or enter a desired pitch shift in semitones to find the required speed ratio.
Reverse: find speed ratio from semitones
Tape speed to pitch formula
Pitch shift (semitones) = 12 * log2(speed_ratio)
Speed ratio = 2^(semitones / 12)
Examples:
speed 2.0 = +12 semitones (octave up)
speed 0.5 = -12 semitones (octave down)
speed 1.498 = +7 semitones (perfect fifth)
The base-2 logarithm converts the linear speed ratio into an octave count, which is then multiplied by 12 to get semitones. This is the same relationship as the equal-temperament pitch formula.
Common tape speed shifts
- Speed 2.0: octave up (+12 semitones). Classic chipmunk effect.
- Speed 0.5: octave down (-12 semitones). Deep, dark, slowed-down effect.
- Speed 1.059: exactly +1 semitone. Subtle pitch raise.
- Speed 0.944: exactly -1 semitone. Subtle pitch lower.
- Speed 1.5: approximately +7 semitones (perfect fifth). Common varispeed tuning.
Tape speed pitch: frequently asked questions
How does tape speed affect pitch?
Tape recorders play back audio at a fixed reference pitch when running at the correct speed. Playing the tape faster increases both the speed and the pitch proportionally. Doubling speed doubles frequency, raising pitch by one octave. Halving speed lowers pitch by one octave.
What is the formula for tape speed to pitch shift?
Pitch shift (semitones) = 12 * log2(speed_ratio). If the playback speed is 1.5 times the record speed, the pitch rises by 12 * log2(1.5) = 12 * 0.585 = 7.02 semitones (approximately a perfect fifth).
How do digital pitch shifters relate to tape speed?
Digital varispeed and pitch-shifter algorithms mimic the tape effect. A digital pitch shift of +7 semitones corresponds to a speed ratio of 2^(7/12) = 1.4983. Many DAWs implement tape varispeed this way.
What speed ratio produces a perfect fifth shift?
A perfect fifth = 7 semitones. Speed ratio = 2^(7/12) = 1.4983. So tape running at approximately 1.5 times normal speed gives a perfect fifth pitch increase.
How is tape speed pitch shift used creatively?
Classic uses: recording at half speed and playing back at full speed (Chipmunk effect), slowing tape for deep de-tuned bass sounds, and creating subtle varispeed fluctuations for lo-fi aesthetics. The same formula applies to DAW time-stretch and varispeed functions.
Official sources
- Audio Engineering Society (AES): aes.org - tape recording and audio standards.
- MIDI Association: midi.org - pitch and semitone specifications.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.