Four ways to change the speed
Four tools move the tempo, and they differ in what happens to the pitch. Slowed + reverb lowers tempo and pitch together and adds space, so the voice gets deeper and the whole track sounds dreamier. Sped up audio does the opposite by default: faster and higher, with a switch if you would rather keep the original pitch. Nightcore pushes further, 105 to 160 percent, and adds a little brightness and bass on top.
The speed changer is the practical one. It runs from a quarter speed to four times, and it keeps the pitch unchanged unless you turn that off, so it suits practice, transcription and fitting a clip to a time slot. If you only want a different key, the pitch changer moves the song by semitones and cents while the tempo stays put.
Loudness: volume, normalize and bass
The volume booster is a blunt, useful instrument: choose a number of decibels, optionally let the limiter catch peaks, and the whole file gets louder or quieter by that amount. The normalizer is a measuring tool. It reads the loudness or the peak of your file and applies the single gain needed to reach a target, so ten files can end up at a similar level.
Pick volume when you know how much you want to change, and normalize when you know where you want to land. The bass booster is separate from both: it lifts only the frequencies below a chosen point, with its own output level so the extra low end does not push the track into distortion.
Space, motion and shape
Reverb places the sound in a room, hall or canyon and can add a repeating echo. 8D audio sends the sound around your head by panning it between left and right, which only works properly on headphones. Reverse audio plays the whole file backwards and has no settings, handy for risers and odd transitions.
Fade in and out smooths the edges of a clip with a choice of curve, and is usually the last touch before you share something. Whatever you build, keep playback at a comfortable level when you test bass or 8D on headphones.
Where to start
For a lo-fi or dreamy edit, begin with slowed + reverb, then move to the bass booster. For a hyped version, try sped up audio or nightcore. For a clean fix to a quiet recording, go from the volume booster to the normalizer. Every page ends with links that carry your result forward, so you can combine them without saving in between. To stack several effects in one go, the studio on the home page chains up to eight modules, each with a bypass LED, and closes the chain with a limiter.