slowed+reverb

About

slowed-reverb.com is a set of free audio tools for making slowed + reverb, sped up, nightcore, daycore, 8D, vaporwave and lo-fi versions of songs. It was built because most tools for this either upload your music to a server, hide basic controls behind a paywall, cap file sizes and daily use, or offer a single “reverb” slider and nothing else.

How it works

Everything happens in your browser. When you open a song, it is decoded on your device with the browser’s built-in audio engine, or with a WebAssembly build of FFmpeg for rarer formats. The effects run on the Web Audio API, time-stretching and pitch-shifting use the Signalsmith Stretch library, and exports are encoded locally (MP3 with LAME, AAC/FLAC/video through WebCodecs or WebAssembly encoders via Mediabunny). Your audio is never sent anywhere.

What we care about

  • Sound quality. Exports use a band-limited resampler for speed changes, a limiter to prevent clipping, and up to 320 kbps MP3, 24-bit WAV, lossless FLAC or 1080p video.
  • Privacy. No uploads, no accounts, and no advertising trackers. See the privacy policy.
  • Control. Every parameter a creator might reach for, with sensible presets so you don’t have to touch them.
  • Honesty. We explain the copyright side of posting edits instead of pretending it doesn’t exist.

Open-source credits

Built with Astro, Signalsmith Stretch (MIT), Mediabunny (MPL-2.0) with its LAME, FLAC and AAC encoder extensions, and ffmpeg.wasm. Fonts: Anybody and Atkinson Hyperlegible Next (SIL Open Font License).

Example music

The before/after examples and the sample song use music that its creators released into the public domain under CC0 1.0. Credit isn’t required, but it’s deserved:

Every processed version was rendered by this site’s own engine, exactly as it would be for your files.

Contact

Found a bug, have a feature request, or a file that won’t open? Email hello@slowed-reverb.com.