Split Stereo to Mono Channels

Stereo sounds like one recording, but it is stored as two separate lists of samples, left and right. In music they usually carry a mix that differs a little from side to side. In field recordings and interviews they often carry two entirely different things. A single microphone for each speaker, a close microphone and a room microphone, a clean take and a backup take. When that happens, the file you want is one channel only, and the other is noise or somebody else. This page writes each channel to its own mono file.

What splitting does

The tool reads the first two channels of the decoded file and writes each one as a mono file with the same sample rate and length. Nothing is mixed or filtered, so in WAV the result is an exact copy of that channel. A stereo file is simply twice the data of mono at the same length, so each mono file is about half the size of the original.

A worked example

Press Sample for a four-second stereo arpeggio and look at the two waveforms: the left plays the notes low, the right plays them an octave higher. Press Split into two mono files. The page offers sample-song-left.wav and sample-song-right.wav, each with one channel and 176,400 frames at 44,100 Hz, 345 KB each against 689 KB for the stereo original. Play them: the left file contains the lower notes, the right file the higher ones, which is how you can tell the channels apart.

Using the two files

For an interview recorded with a microphone per speaker, keep both files and edit each speaker separately, which lets you reduce noise, change levels or remove a cough on one voice without touching the other. If one channel contains a hum from a bad cable, use only the other. For music, the two halves of a stereo mix are not a useful way of isolating instruments; the instruments are spread across both channels.

Choosing a format

WAV keeps the samples unchanged and is the usual input for editors. AAC in M4A and Opus in WebM compress each file separately and are smaller; set a bitrate above 64 kbps for speech or 128 kbps for music. Both mono files use the same settings, and each has its own download button once ready.

Edge cases

If the file has one channel, the tool tells you that there is nothing to split. If it has more than two, such as a 5.1 mix, only the first two (front left and front right) are written. Channels that are identical produce identical files. A phase-inverted channel would sound normal alone but cancel when the two are added, which the phase inverter tool can fix.

Limits

The tool cannot unmix instruments or voices that were mixed into both channels, nor does it re-balance or normalise the levels of the split files. The files are made on your device and nothing is uploaded; very long recordings are limited by memory.

Related tools

• Audio Phase Inverter & Mid/Side Decoder fixes channels that cancel when combined.
• Merge & Join Audio Files joins processed channels or clips again.
• Audio Converter mixes a file down to mono instead of splitting it.
• Audio Cutter trims a split channel.