Slow down a song without changing the pitch. Or speed up a podcast.
Slow down a guitar solo to learn it. Drop a piano piece to half speed and transcribe it by ear. Speed up a 2-hour lecture to 90 minutes. Pitch stays in key (time-stretch) or rides with the speed (tape effect) — your call. Browser-only, never uploads.
drop audio here
MP3, WAV, M4A, FLAC, OGG, AAC, video. Drop several for batch.
Pitch-preserved vs. pitch-shifted
Keep pitch uses time-stretching: speech and music sound natural just faster or slower, like a podcast player on 1.5×. The math is slightly heavier (we use FFmpeg's atempo filter), so the first run loads the codec.
Pitch + speed just plays the samples faster or slower, like a tape sped up. Vocals go chipmunk at 2× and slow drawl at 0.5×. Useful for effects, transcription of pitched material, or matching a sample to a different key.
Common use cases
- Learning a guitar solo: 0.5–0.75× with pitch preserved. The key stays the same so you can play along.
- Transcribing a piano or bass part by ear: 0.5× pitch preserved reveals notes you can't hear at full tempo.
- Drum fill breakdown: 0.6× pitch preserved to map the kick / snare / ghost notes.
- Slowing down a fast talker for transcription: 0.75–0.9× pitch preserved.
- Speeding up podcasts and lectures: 1.25–1.5× pitch preserved — the standard "podcast player" effect.
- Speech-language pathology / pronunciation practice: 0.7–0.85× pitch preserved.
- Chipmunk / demon voice effects: 1.5× or 0.5× with pitch shifted (tape effect).
- Matching a sample to a different key: pitch-shifted mode at the speed ratio of the semitone change.
FAQ
How do I slow down a song without changing the pitch?
Drop the song, pick a speed below 1× (try 0.75× for transcribing, 0.5× for note-by-note dissection), and leave the mode on "Keep pitch (time-stretch)." The result plays slower but in the original key.
Best speed for learning a guitar solo?
Start at 0.5× to map the notes, then bump up to 0.75× to drill, then 0.9× to play along. Always keep pitch on — your guitar isn't going to retune for each pass.
Will slowing down a song ruin the sound?
Mild slowdowns (0.6–1×) are nearly transparent. Below 0.5× you start hearing the time-stretch artifact ("phasiness") on cymbals and reverbs. For pure-note instruments like guitar and piano it stays usable down to 0.3×.
What's the quality loss?
Pitch-preserve mode introduces some phasiness at extreme speeds (below 0.5× or above 2×). Within ±50% the result is generally clean.
Why does pitch-preserve take longer than tape mode?
It runs an STFT-based time-stretch algorithm. The first run also loads the codec (~3 MB).
Does my audio upload?
No. Everything happens in your browser tab.