Change Audio Speed
100% private — runs on your device, never uploaded. Works offline once loaded.
Speeding a recording up is how an hour-long lecture or interview becomes forty minutes you will actually finish, and slowing one down is how a musician learns a fast passage or a transcriber catches a mumbled sentence. Both are handled here with the pitch kept natural, so a voice sped up to 1.5× still sounds like the same person rather than a cartoon — the recording is cut into tiny overlapping slices and re-laid closer together, which changes the timing without changing the frequencies. If you do want the old tape-speed effect, where the pitch climbs with the speed, that is one setting away.
How the pitch stays put
Playing a recording faster the old way — spinning the tape quicker — raises the pitch, because every frequency in it rises by the same proportion. Keeping the pitch means separating timing from frequency: the audio is cut into short overlapping windows and those windows are laid down closer together (faster) or further apart (slower), with the overlaps blended so the joins are not audible. The frequencies inside each window never change, so the voice stays the same voice.
It is not free. Push far beyond 2× and the windows start to smear, giving the fluttery, phasey quality familiar from audiobook apps at high speed. Music, with its sustained tones and sharp transients, shows it sooner than speech does.
What people actually use this for
- Getting through a lecture, interview or meeting recording at 1.25× to 1.5× — the range where comprehension is essentially unaffected
- Slowing a musical passage to 0.5× or 0.75× to learn it, with the pitch held so it stays in the same key
- Slowing speech to transcribe a mumbled or accented section by ear
- The deliberate tape-speed effect, where letting the pitch move is the point
Frequently asked questions
Does speeding up hurt comprehension?
Up to about 1.5× most listeners adapt within a minute or two with no measurable loss. Beyond 2× comprehension falls off, especially with unfamiliar material or a strong accent.
Can I keep the key when slowing music down?
Yes — that is the default. The timing changes and the pitch does not, so a slowed passage stays in the same key as the recording.
Advertisement