RunLocalTools

Audio Pitch Shifter — Change Key or Tempo Online, Free & Private

Shift the pitch of any song or voice recording up or down by semitones and cents, change tempo without changing pitch, preview it, and export WAV or MP3. Runs in your browser — nothing is uploaded.

What it does

Load an audio file (or the audio track of a video) and change its key without changing its speed, or change its speed without changing its key. Move the pitch up or down by up to two octaves in semitones, fine-tune it in cents, slow a song to half speed to learn it, or switch to tape-style mode where speed and pitch move together. Preview a section, flip between the original and the shifted version, then export the result as WAV or MP3.

How it works

The tool uses a phase vocoder, a standard technique for changing pitch or tempo independently. It cuts the audio into overlapping windows, analyses the frequency content of each one, and rebuilds the sound with adjusted timing. To keep tones clean it applies identity phase locking, so harmonics stay together instead of turning “phasey”. For stereo and multichannel files, the phase is worked out from all channels together and applied identically to each one, which keeps the stereo image intact.

To shift pitch without changing length, the tool stretches or compresses time by the pitch ratio and then resamples with a windowed-sinc filter. The filter is band-limited first, so shifting up doesn’t create aliasing. An optional formant-preservation mode estimates the spectral envelope of each frame (the vocal-tract “shape” that makes a voice sound like that voice) and corrects it after the shift, so voices don’t turn into chipmunks or giants.

The Engine detail setting trades attack sharpness against smoothness: a smaller analysis window keeps drum hits punchier, a larger one is smoother on sustained notes and low bass. Processing runs in a background Web Worker, so the page stays responsive.

Pitch detection uses the YIN algorithm on the file (or the region you selected) and reports the most common note and how many cents sharp or flat it is. Pick a target note and the tool works out the exact shift for you.

How to use it

  1. Add one or more audio or video files, or record a fresh take first with the Audio Recorder. Files stay in your browser after a refresh until you clear them.
  2. Choose a mode. Keep speed changes only pitch (and optionally tempo). Tape changes pitch and speed together.
  3. Set the semitones, fine tune and tempo, or pick a preset (432 Hz tuning, octave up or down, half-step down, capo transpositions, nightcore, slowed).
  4. To match a specific key, press Detect pitch, then choose a target note.
  5. Drag on the waveform to select a section, then switch to Shifted and press Play. Use Original and Shifted to compare at the same spot.
  6. Choose MP3 (128–320 kbps) or WAV (16-bit, 24-bit or 32-bit float) and press Export. With several files loaded, Export all downloads a .zip with the same settings applied to each. If you’d rather have the shifted clips joined into a single track, run them through the Audio Merger afterwards.

Supported formats and limits

  • Input: anything your browser can decode, typically MP3, WAV, OGG, M4A/AAC and FLAC. Video files (MP4, MOV, WebM) work when your browser can read their audio track, which is most reliable in Chrome and Edge.
  • Output: WAV in 16-bit, 24-bit or 32-bit float (stereo and multichannel are kept), or MP3 in stereo or mono.
  • MP3 notes: MP3 supports mono or stereo only, and a fixed set of sample rates. Surround files are downmixed to stereo and unusual rates (such as 96 kHz) are converted to the nearest supported rate, for MP3 only. WAV keeps your channels.
  • Sample rate: audio is decoded at your browser’s audio rate, usually 44.1 or 48 kHz.
  • Very large files use a lot of memory. The tool warns you before you add them.
  • Like every phase-vocoder tool, very sharp percussive attacks are softened a little, more so at large shifts. Choose a smaller Engine detail for drums.

Privacy

Your audio is processed entirely on your device. It is never uploaded, and nothing you load is sent to a server.

  • Local: decoding, pitch shifting, tempo change, pitch detection, preview and WAV export.
  • Uses the internet, once: the first MP3 export downloads a small open-source MP3 encoder from a public CDN, then works offline. The library is fetched; none of your audio is sent. Batch .zip downloads likewise fetch a small ZIP library the first time.
  • Saved files: your audio and settings are kept in your browser’s own storage so a refresh doesn’t lose your work. Press Clear saved files to remove them.

Frequently asked questions

Does changing the pitch change the length of the song?

Not in Keep speed mode. Pitch changes while the duration stays the same, unless you also move the tempo slider. In Tape mode the two are linked, like speeding up a record, so a higher pitch is also faster.

How many semitones can I shift by?

Up to 24 semitones (two octaves) in either direction, plus up to 100 cents of fine tuning. Small shifts of a few semitones sound the most natural. Very large shifts are more audible as processing.

How do I convert music from 440 Hz to 432 Hz tuning?

Pick the A440 → 432 Hz tuning preset. It lowers the pitch by about 31.8 cents, the exact ratio between the two tunings.

How do I slow a song down to learn it without changing the key?

Set the tempo slider below 1× (0.5× is half speed) and leave the semitones at 0. Select the tricky section on the waveform and turn on Loop to practise it repeatedly.

Why does my voice recording sound odd after shifting?

Voices have resonances that shouldn’t move when the pitch moves. Turn on Preserve formants and the tool corrects for it. If the recording also has loud and quiet moments, even them out first with the Voice Recording Audio Normalizer so the shift works on a consistent level. For very large shifts on voices, keep the shift under about 5 semitones for the most natural result.

Can it detect the key of a whole song?

Pitch detection is designed for a single voice or instrument. On a full mix with several notes at once it may report nothing or an unhelpful result, and the tool will say so. Select a region with one clear melody line, or type the shift in by hand.

Is there a file size or length limit?

There’s no fixed limit, but decoded audio is held in memory, so very long files (an hour or more) may be slow or fail on phones. Working on a shorter clip is faster.