Slowed + Reverb Maker

Turn any song into the dreamy "slowed + reverb" style: a little slower and deeper, washed in a long, soft reverb. Or go the other way for a bright sped-up or nightcore edit. Choose the speed, how much reverb and how long it rings, and add a touch of bass if you like. The song is processed in your browser and never uploaded.

How to use this tool

1. Choose one or more songs.
2. Set the speed: 0.85 is the classic slowed sound; 1.3 with reverb 0 gives a sped-up version.
3. Choose the reverb amount (around 30%) and length (2–4 seconds), and an optional bass boost.
4. Press Calculate, listen, and download the MP3 or WAV.

Formula

New length = original length ÷ speed + reverb length · pitch change = 12 × log2(speed) semitones

The speed is changed by band-limited resampling, like playing a record slower or faster, so pitch and tempo move together: 0.85× lowers the song by about 2.8 semitones. The reverb is a convolution with a generated stereo impulse response: decorrelated noise in each channel with a 20 ms pre-delay, falling by 60 dB over the reverb length and softened above about 5 kHz. The mix uses √(1 − reverb) for the dry sound and √reverb for the reverb. If the result would peak above −1 dBFS it is lowered to fit, and MP3 files are checked again after encoding.

Example

A 3:20 song (200 s) at 0.85× becomes 200 ÷ 0.85 = 235.3 s long, plus a 3 s reverb tail: 238.3 s (3:58). It sounds 12 × log2(0.85) = 2.8 semitones lower. At 1.3× with no reverb it would last 153.8 s and sound 4.5 semitones higher.