Reverse Audio

Reversing is one of the oldest effects there is, and almost every use of it is a specific job rather than a novelty. These are the ones people actually arrive with.

• Reverse cymbals and risers. Flip a crash or a piano chord and it swells into the downbeat instead of decaying away from it. Marking just that one hit and leaving the rest of the track alone is what makes this practical.
• Backmasking. Hide a phrase so it reads forwards when the track is played backwards, or find out what a famous one actually says.
• Reverse reverb. Reverse a vocal, add reverb to the reversed version, then reverse it back — the tail arrives before the word instead of after it.
• Boomerangs and loops. A palindrome plays forwards and then backwards, so a short clip repeats without ever reaching an edge.
• Sound design. Reversed speech, reversed foley and reversed room tone are the fastest route to something that sounds unfamiliar without sounding processed.
• Finding an edit point. Played backwards, a transient you cannot hear in context becomes obvious.

Most online reversers do one thing: flip the whole file. That is the least useful of the three, and it is the only one most of them offer.

• The whole track. Every sample in the opposite order. The length does not change, because a reversal moves samples rather than adding or removing them.
• A marked section, in place. Drag across the waveform to mark a span. That part is flipped and everything on either side of it is left exactly as it was, so a reversed cymbal sits inside a finished mix rather than replacing it. Mark several spans and each is reversed independently. The length still does not change.
• A palindrome. The track forwards and then backwards, or backwards and then forwards. The result is close to twice as long, and an overlap control lets the two halves cross into each other so the turn is tighter.

Two of the tools that do offer a section reverse hand back only the section, which means rebuilding the track around it afterwards. Reversing in place is what a desktop editor does with a selection, and it is what this tool does.

A palindrome sounds like it should need a crossfade to hide the turn. It does not, and the reason is arithmetic rather than processing.

Playing a track forwards and then backwards puts its last sample next to itself at the turn, and its first sample next to itself where the file repeats. Both joins are therefore continuous by construction — there is no step to hide, because the two sides of each join are the same value. Measured on this tool, the movement across both joins is no larger than the ordinary sample-to-sample movement inside the audio itself. The overlap control is not there to fix a click; it is there when you want the turn to be shorter and tighter, and it makes the file shorter by exactly the amount you set.

A reverse is a permutation: the same samples, in the opposite order. Nothing is filtered, resampled or recomputed, so the only thing that can cost quality is the format you write to.

• WAV and FLAC are exact. Reverse a file and reverse the result, and you get the original back sample for sample — no difference at all, not a small one. That is checked on every build, with a lossy round trip as the control to prove the check can fail.
• MP3, AAC, M4A and OGG re-encode. That costs a generation, the same as it would in any tool. If the source was already lossy it is usually still fine; if it was a master, choose FLAC.
• The sample rate is left alone by default. A reverse has no business changing how many samples there are per second, so nothing is resampled unless you ask for it.
• The length is checked, not assumed. A whole-track or section reverse comes out exactly as long as it went in, and a palindrome exactly twice as long minus the overlap. The finished file is measured against that before it is handed to you.

Powered by optimised audio processing algorithms.

• Mark the section a little wide. A reversed cymbal wants the whole tail. Include the decay you are flipping and the transient that starts it.
• Use FLAC if you are going to reverse it again. Reverse reverb means reversing twice. Two lossy generations are audible; two lossless ones are not, because there is nothing to lose.
• Add the fade after the reverse, not before. The fades here apply to the finished file, so a fade-out lands at the real end of a palindrome rather than in the middle of it.
• Turn tags off for sound design. A reversed cymbal does not need the album name of the record it came from attached to it.
• Reverse the whole thing to find the edit. If you are hunting for the exact point a note starts, flip the track, listen for where it stops, and read the position off the waveform.

• Audio Cutter
• Audio Speed Changer
• Fade Audio
• Audio Converter
• Audio Reverb
• Audio Merger