Audio Tempo Changer
Make decoded audio slower or faster while approximately preserving pitch using MesraTools' browser overlap-add (OLA) foundation.
0.50× = about twice as long; 2.00× = about half as long.
What this tool does
It changes duration/tempo without intentionally transposing musical pitch. Build 106 uses a lightweight overlap-add algorithm intended for useful browser processing, not a professional phase vocoder or studio-grade time-stretch engine.
When to use it
Use it for speech practice, rough timing changes, rehearsal assets or compatibility workflows where a local browser result is useful. Extreme changes can create echo, smearing or transient artifacts.
Tempo is not playback-rate pitch shift
A simple playback-rate change alters both duration and pitch. This tool instead uses overlap-add to approximately retain pitch while changing duration. For deliberate transposition, use Audio Pitch Shifter.
Privacy, output and limits
Processing stays in the browser. Output is a new 16-bit PCM WAV. ID3 tags, artwork and compressed-codec metadata are not preserved. Results depend on source material and are not claimed to equal DAW-quality stretching.
Example
A 60-second clip at 1.25× targets roughly 48 seconds while keeping musical pitch approximately unchanged.
FAQ
Will voices sound perfect? Not always; OLA can produce artifacts. Does this change sample rate? The exported WAV keeps the decoded sample rate.
Related tools
Audio Pitch Shifter, Audio Sample Rate Converter, Audio Trimmer and Silence Trimmer.