Slow Down Audio Without Changing Pitch

Speed multiplier guide:

• ·0.75× (75% speed) — Barely perceptible slowdown. Good for following along with fast speech or catching missed words in a conversation.
• ·0.5× (half speed) — The standard for music learning and transcription. Clear enough to distinguish individual notes and phonemes; minor time-stretch artifacts in complex audio.
• ·0.33× (one-third speed) — Appropriate for very fast passages or detailed phonetic analysis. Artifacts more noticeable; use headphones and expect some "swimmy" sound.
• ·0.25× (quarter speed) — Maximum practical slowdown. Heavy artifacts in music; still usable for isolating individual syllables or notes.

Pitch correction: The tool preserves pitch at all speeds by default. If you specifically want the tape-slow effect (pitch drops with speed), disable pitch preservation in the settings.

Format recommendation: For music learning, WAV or FLAC sources give the cleanest slow-down results — more audio data means the time-stretch algorithm has more to work with. MP3 at very low bitrates (below 128 kbps) can show additional artifacts when time-stretched.

Preview strategy: Set the speed and listen to a representative 10-second section before processing the whole file. Speed processing is the one operation where the preview matters most — the result sounds substantially different from the original.

Slow-down vs pitch shift: Slowing down audio changes the timing without changing pitch. Pitch shifting changes the frequency content without changing the duration. They are independent parameters. This tool addresses timing (speed) only; the Pitch Shifter tool handles frequency (pitch) independently.

0.5× browser time-stretch vs dedicated transcription apps: Apps like oTranscribe, Transcriber Pro, and Descript offer slow-down alongside automatic transcription, foot pedal support, and text-sync. If you are transcribing professionally, a dedicated tool adds significant workflow efficiency. This browser tool is the right choice for one-off slow-down of any audio file without signing up for a service.

Time-stretching quality in browsers: Browser-based time-stretching uses the Web Audio API's playback rate with pitch correction, or a JavaScript implementation of phase-vocoder algorithms. Quality is acceptable for learning and transcription — comparable to early desktop implementations like early Audacity or WMP's playback controls.

Slowing down audio without time-stretching produces the familiar tape-slow effect: the pitch drops along with the speed, turning speech into a deep rumble and music into a sluggish, detuned version of itself. This is only useful as an artistic effect — not for learning or transcription.

Modern time-stretching algorithms separate speed from pitch mathematically. By dividing the audio into short overlapping windows, shifting the timing of those windows, and blending them back together, the algorithm changes the temporal position of sounds without altering their frequency content. The result sounds like the original — at the right pitch — just slower.

The most common uses are ear-training and music transcription (learning a fast guitar solo or piano run at half speed before playing at full tempo), language learning (slowing down a native speaker's pronunciation to catch every sound), and transcription work (making spoken content slow enough to type in real time).

The quality of the slow-down depends on the algorithm and the reduction amount. At 0.75× (three-quarters speed), the output sounds clean and natural. At 0.5× (half speed), minor artifacts appear in complex audio — they are noticeable but acceptable for learning purposes. Below 0.5×, artifacts become more significant and the sound becomes "watery" or phasic.