A phase vocoder, as commonly used to slow down audio without changing the pitch for transcription purposes, to change the apparent gender of a speaker, to make a musical segment fit alongside other tracks and in other artistic and wacky applications.
I will, in addition to pre-recorded file support, add support for live mic input soon, so as to provide the 'voice-changing' functionality (well, you'll be able to change the pitch of live input, but not the duration - that'd break the laws of time 😉).
There is nothing to install and nothing further is downloaded or uploaded once the initial page loads: the app is ready to go. A sample wave file is loaded into the wave display to start with (this is from the Berklee College Sampling Archive, licensed under https://creativecommons.org/licenses/by/3.0/deed.en_US), but you can choose from any audio files you have in your possession.
Use the Open button to select a wave file, or drag and drop onto the wave display. Click on the waveform to play without looping, or click the Loop button (or hit the Space bar) to loop playback (press Space again to stop playback). You can adjust the red L/R markers to delineate the loop.
Clicking the Save button will save whatever is between the L and R markers with the settings applied.
Waveform view and playback powered by wavesurfer.js, licensed under https://creativecommons.org/licenses/by/3.0/deed.en_US, with modifications by myself.