Slow down or speed up audio from 0.5× to 2× while preserving the original pitch. Hear tempo changes live, seek the waveform and preview the actual exported WAV.
No file selected.
Up to 128 MiB per file; decoded audio up to 256 MiB (about 23 min mono / 11½ min stereo). Formats depend on your browser's decoder. Working audio and WAV exports use 48 kHz.
Choose audio to begin. Nothing plays automatically.
No audio loaded
Your waveform will appear here.
Load audio to choose a section.
Click the waveform to seek the source; use Play/Pause, exact time or jump controls. Tempo changes apply live while playing. Pitch is preserved; the waveform remains the original source. The source ruler always shows original source time.
Playback stopped.
Change the tempo while playing to hear it immediately. Uncheck to compare original tempo; exports always use the chosen tempo.
The original file stays unchanged.
Input up to 128 MiB; source and rendered float audio each have a 256 MiB limit. Slowdowns may exceed the output budget even when live preview works. Tempo uses floating-point precision; duration rounds up to a whole sample. Live changes may take a short processing buffer to become audible.
Create a WAV to preview the actual adjusted file.
48 kHz · 16-bit PCM WAV · original channel count. Browser decoding may resample input. Pitch-preserving WSOLA time stretching uses SoundTouchJS; no normalization, BPM detection or beat alignment is added. Stretching can change peaks; out-of-range samples are clipped and counted. Tags/artwork are omitted. Changing settings clears old exports. Export runs in a cancellable local worker. Pitch preservation is an algorithmic approximation; inspect and listen to the actual result.
Your audio is never uploaded to any server. Decoding, pitch-preserving time stretching, playback and WAV encoding run locally with self-hosted SoundTouchJS code. Source files remain unchanged.
Tempo Changer uses WSOLA time stretching to preserve the original pitch while changing duration. Audio Speed Changer changes pitch and speed together. Pitch preservation is approximate: large changes can soften transients or introduce warbling and other artifacts.
Yes. Tempo updates apply to the playing local AudioWorklet without restarting the source. A short processing buffer can delay an audible change. Seeking or resuming starts a fresh processing region, so boundary sound can differ from continuous playback. Fixed-tempo preview and export use the same WSOLA engine; actual WAV export is the final result.
No. The multiplier is relative to the chosen source. No BPM detection, beat alignment, normalization or formant correction is added. Source waveform and seek time remain in original seconds; the exported player uses adjusted seconds.
Tempo ranges from 0.5× to 2×. Input is one file up to 128 MiB, mono/stereo, decoded at 48 kHz within a 256 MiB float buffer. Adjusted output has its own 256 MiB float budget; slowdowns can exceed it even when live preview works. Browser/device memory can impose lower limits. AudioWorklet requires a supported browser and HTTPS or localhost. Export is 48 kHz 16-bit PCM WAV with original channel count; tags/artwork are omitted.
Yes. Stop export or changing settings terminates the local processing worker and discards obsolete results. Downloads enable only after the actual generated WAV preview loads. Final duration rounds up to a whole sample; out-of-range samples are clipped and counted.
