Reverse Audio

Reversing a sound is one of the oldest tricks in audio. Run a tape backwards and a cymbal crash becomes a swell that builds into a hit, a vocal phrase turns into a ghostly murmur, a piano note sucks inward. Producers use it to make risers, transitions and eerie textures, and curious listeners use it to hear what a recording sounds like from the other end. In digital audio it is simply the list of samples read from the last to the first.

What reversing does

A recording is a long list of numbers, one per sample per channel. Reversing writes the same numbers in the opposite order. Nothing is added or removed, which is why the length, the sample rate and the quality in a lossless format are unchanged. The sound’s shape in time is mirrored: the attack, the sharp start that gives an instrument its identity, ends up at the finish, and the decay, a gradual fade, becomes a gradual build.

A worked example

Press Sample to load a four-second stereo arpeggio of four plucked notes followed by a chord. Press Reverse and the page writes sample-song-reversed.wav with 176,400 frames at 44,100 Hz, two channels, 689 KB: the same as the original. When you play it, the chord now comes first, swelling in rather than dying away, and the four notes follow in reverse order, each gliding up to a sudden end. Tick Play the original first, then the reversed sound and the file doubles to eight seconds, which makes an echo-like back-and-forth.

Typical uses

For a reverse cymbal, take a crash, reverse it and place it so its loudest moment lands on the downbeat of the next section. For reverse reverb, reverse a vocal phrase, add a long reverb to it, then reverse it again: the reverb now builds up before each word. This tool does the reversing step; you would use your editor for the reverb. A reversed sound effect from your own voice can also make an alien language for a game or a short film.

Edge cases

Very quiet starts become very quiet ends, so reversed clips may finish abruptly if the original had a sharp attack; add a fade-out in your editor if the cut is unpleasant. Files that start with silence end with silence. Long files are reversed in memory, so the limit is your device’s available memory. Stereo files keep their left and right channels, and surround files are handled channel by channel.

Limits

The tool flips the entire file and does not offer a region, a crossfade or a fade. Lossless output (WAV) gives an exact reversal; Opus and AAC encode the reversed sound again and lose a little detail. Nothing is uploaded, and the player on the page is for checking the result before you download it.

Why reversed sound behaves the way it does

Most natural sounds start sharply and fade away: a struck piano string, a snare hit, a spoken consonant. Reversed, the same sound swells slowly and ends abruptly, which is the idea behind the reverse cymbal and the reverse reverb used in production. Because the page only changes the order of the samples, reversing a file twice gives back the original order, and the source file is never altered, so you can experiment freely and keep the original beside the result.

Related tools

• Audio Cutter selects the part of a recording to reverse.
• Merge & Join Audio Files puts the reversed part back into a longer piece.
• Audio Speed & Pitch Changer slows or pitches a reversed sound for sound design.
• Voice Recorder records a phrase to turn backwards.