Grainfreeze Tonality Preserving Spectral Freeze VST (Free Windows VST, Open Source for Win/Mac/Linux)

See it in action:

Grainfreeze is a real-time phase vocoder–based time-stretching and freeze processor. It loads an audio file into memory and resynthesizes it using FFT analysis and overlap-add techniques. You can click and drag around the playhead freely as you wish, moving it backwards plays the sound grains backwards as well, and have various controls for the playback speed and sound smoothing. Arguably the most interesting possibility is the spectral freeze mode, here a tiny slice of the audio gets looped using crossfading.

Grainfreeze is inspired by the Audiostretch App from Bandlab. As there is no real VST or standalone program equivalent for this kind of tonal zero playback speed sound freezing, I made this with the help of Claude Sonnet 4.5 AI and lots of tinkering around. I have not had a great look at the FFT algorithm it implemented, but I bundled the source code written in JUCE/C++ together with the download, so if you're a pro at this stuff you might be able to improve it further - it is completely open source :)

Please note that the focus is on the preservation of tonality, not transients which will get heavily smeared.