What is the formula for pitch shifting?

The playback speed multiplier is 2 raised to the power of (semitones / 12). For example, shifting up 12 semitones (one octave) gives a multiplier of 2.0 — double speed. Shifting down 12 gives 0.5 — half speed.

What is the difference between the two FFmpeg commands?

The "Speed + Pitch" command changes sample rate with asetrate, then resamples to the original rate, so pitch and duration change together. The "Pitch Only" command uses the optional rubberband filter to shift pitch while keeping tempo.

Does rubberband need to be installed separately?

Yes. On Ubuntu/Debian run: sudo apt install librubberband-dev. On macOS with Homebrew: brew install rubberband. Then rebuild FFmpeg with --enable-librubberband, or install a pre-built FFmpeg that includes it (e.g. via Homebrew ffmpeg on macOS).

How many semitones are in an octave?

An octave spans exactly 12 semitones. Shifting by +12 semitones doubles the frequency; shifting by -12 halves it.

Can I shift by fractional semitones?

Yes. This tool accepts decimal values such as 0.5 (a quarter-tone) or -1.5. The 2^(n/12) formula works for any real number.

Audio Pitch Shifter

Enter semitones to shift, get the speed multiplier and FFmpeg commands to pitch-shift audio files offline.

Pitch Shift Settings

Semitones to shift

Positive = pitch up, negative = pitch down. Decimals allowed (e.g. 0.5).

Input filename (for the FFmpeg command)

Input sample rate (Hz)

Use ffprobe to confirm the source rate; common values are 44,100 and 48,000 Hz.

Quick pick (semitones)

Speed Multiplier

1.0000 × original speed

No pitch shift (0 semitones).

Frequency Ratio

1.0000 × original pitch (Hz)

Same value as speed multiplier — doubling frequency = one octave up.

FFmpeg — Speed + Pitch

Changes both pitch and tempo (shorter/longer playback).

FFmpeg — Pitch Only (rubberband)

Shifts pitch while keeping original tempo. Requires FFmpeg built with librubberband.

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Summary

Enter semitones to shift, get the speed multiplier and FFmpeg commands to pitch-shift audio files offline.

How it works

Enter the number of semitones to shift (positive = up, negative = down).
The speed multiplier is calculated instantly using the 2^(n/12) formula.
Choose whether to preserve the original tempo using the rubberband filter.
Copy the FFmpeg command and replace "input.mp3" with your actual filename.
Run the command in your terminal to produce the pitch-shifted audio file.

Use cases

Transpose a song to match a singers vocal range.
Create harmonies by copying an audio track and shifting it by thirds or fifths.
Shift audio down 12 semitones to create deep vocal drops or sub-bass effects.
Adjust the key of a backing track without re-recording.
Verify tuning: shift 12 semitones should sound exactly one octave up.
Prepare stems for remixes that need to be in a different key.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu