Reduce the amount of audio channels
Downmix an audio track to mono by selecting 1 channel in the output settings.
Downmix an audio track to stereo by selecting 2 channels in the output settings.
By submitting a mono file and selecting 2 channels, the audio will instead be upmixed to stereo.
Select an audio file that you want to downmix.
Select the amount of channels that you want to downmix to.
Let the file be processed and you can download your modified file right afterwards.