Free tools for your next audio edit
Change a short recording from half speed to double speed while preserving its pitch. Choose an MP3 or WAV, prepare the new file locally, then preview and download the actual export. No account, credits, or audio upload needed.
No file selected. Audio stays in this browser.
Pitch-preserving time stretching can alter attacks, texture, and timing. The processor retains its nonzero PCM tail, so the actual duration can slightly exceed source duration divided by speed. Input and processed output are limited to five minutes; WAV output is also limited to 50 MiB. At 1×, stretching is bypassed, but decoding and export still apply. Keep your original.
Hear the phrase at your pace
Prepare a saved recording you can use. Choose a short phrase for practice or review rather than repeatedly encoding a complete recording.
Open mono or stereo audio up to 50 MiB and five minutes. Preview the original to identify the phrase. Your audio stays in the browser.
Try 0.75× for a slower practice copy, 1.25× for a modest increase, or another setting. Select WAV for editing or MP3 for a compressed copy, then prepare the export.
Compare with the original, including the opening and ending. The preview plays the same file you download. Check the displayed processed duration and save the result before leaving.
Time stretching, explained
A pitch-preserving speed change makes a phrase longer or shorter without intentionally moving its notes up or down. This tool overlaps short sections of the decoded recording to stretch time. It processes both stereo channels together, retaining their left and right positions.
For example, a 30-second excerpt at 0.75× has a nominal duration of 40 seconds. At 1.5×, its nominal duration is 20 seconds. A short processed tail may extend the actual duration; the tool retains it and reports the actual processed frame count. MP3 can add further encoding delay or padding.
This differs from changing only a raw playback-rate setting. MDN’s playbackRate reference describes resampling at a different rate, which also changes pitch. Here, pitch-preserving processing is applied to the exported file, rather than relying on a player setting that disappears after download.
Choose a useful working copy
Make a slower copy to follow the rhythm and notes. Start near 0.75× and listen for altered attacks or a grainy texture. This tool does not detect BPM or promise an exact musical tempo. Use the audio trimmer first to isolate the passage in time.
Slow a short passage to follow unfamiliar wording, or speed up a clear recording for review. It does not transcribe, translate, repair missing words, or remove overlapping speakers. Keep enough surrounding context to understand the passage.
Try a different duration for an existing effect. Every audible source changes speed together. If you need one effect from a mix, use the separate AI sound-effect extractor first; that service has its own account and credit requirements.
Listen before placing the result
Time stretching can change transient detail, texture, and the shape of a sound’s beginning or ending. Large speed changes are more demanding. Pitch preservation does not mean lossless processing or identical sample peaks. At 1×, stretching is bypassed; decoding and export still apply.
The browser decodes at 48 kHz. WAV writes 16-bit PCM; MP3 applies a new lossy encode at 128, 192, or 320 kbps. Original tags, artwork, and source bit depth are not copied. Samples beyond integer PCM range are clipped during export. Use the loudness meter to inspect a new copy when levels matter.
Both input and processed output are limited to five minutes. Slowing a five-minute recording to half speed would require about ten minutes, so it is rejected. WAV output must also fit within 50 MiB. Trim the original to a shorter excerpt when needed. If the retained processed tail would exceed a limit, the export fails instead of silently cutting it.
Each preparation starts from your original. Changing a setting clears the previous result, and cancelling discards pending work. Download before reloading or leaving. Processing uses the pinned SoundTouchJS Stretch engine; version, license, and corresponding source records are available.
A few useful answers
Choose a supported mono or stereo MP3 or WAV, select a speed below 1×, and prepare the export. The tool uses pitch-preserving time stretching rather than simply lowering the playback rate. Listen to the actual WAV or MP3 before downloading; stretching can change attacks and texture.
Yes. Processing and downloads are free, with no account or audio upload. Your browser decodes the selected file and processes it in a local worker. The separate AI isolation service has its own account and credit requirements.
Yes. Choose any speed from 0.5× to 2× in 0.05 steps, or use a preset. Values above 1× make the recording shorter and faster; values below 1× make it longer and slower. Both preserve pitch rather than deliberately shifting it.
Input must be a supported mono or stereo MP3 or WAV up to 50 MiB and five minutes. Processed output is also limited to five minutes, and WAV output to 50 MiB. Slowing down a long file may exceed those limits; use a shorter excerpt or a faster speed. The tool rejects an oversized output instead of cutting it.
That calculation is the nominal duration. Time stretching can leave a short processed tail beyond it. The tool retains nonzero PCM tail samples and reports the actual processed duration instead of silently cropping them. MP3 can add further encoding delay or padding, so processed PCM timing is not a measurement of the final MP3 duration.
No. Each export starts from your selected original, which is not overwritten. All sounds in the recording change speed together. The tool does not isolate a voice, remove noise, detect BPM, or match an exact musical tempo.
WAV writes 48 kHz, 16-bit PCM with the decoded mono or stereo layout. MP3 offers 128, 192, or 320 kbps and applies a new lossy encode. Browser decoding can resample the source; original tags, artwork, and bit depth are not retained. Keep the original and choose WAV when precise placement matters.
The stretching engine is bypassed. The browser still decodes the file at 48 kHz and exports a new PCM WAV or encoded MP3, so 1× is not a byte-for-byte copy of the original.
After preparing your audio