If the video contains more than one available audio track, use AudioCut’s track selector and listen after the new track loads. Check its name, language and codec when those details are present. Export uses the selected track, not a mix of every track.
Check whether there is more than one track
A video may carry one soundtrack, several language versions or an additional commentary track. It may also contain no usable audio. The filename cannot reliably tell you which case applies.
Open the local video in MP4 to MP3. Once the file is decoded, look for the track control in the editing settings. A selector is shown when multiple tracks are available; a single-track file does not need that control.
Use the labels, then listen
Track names and language metadata can be missing or ambiguous. A codec label describes how the sound is encoded, not whether it is the performance or language you wanted. Treat the labels as a starting point.
Switch to the intended track and wait for it to load. Listen to a passage with recognizable speech. If it is silent, check the original in another player and try the other available track rather than increasing gain immediately.
Review editing decisions after switching
Each track can differ in content and timing. After changing tracks, check the waveform, the export range and any cuts before exporting. Do not assume a decision made against one language version belongs at the same point in another.
Export produces an audio-only MP3 of the selected, edited track. It does not preserve the video picture, combine commentary with the main soundtrack or create a new multilingual video file.
If the track cannot be read
An available track can still use a codec the current browser cannot decode. A decoding error is not proof that the track is empty. If possible, export a compatible audio version from the app that created the video.
Do not rename the video extension to MP3 as a workaround. The container and codec need to be read and the output needs to be encoded correctly.
Questions about this task
Why is there no track selector?
It appears when more than one track is available. The source may have only one usable track, or loading may not have completed.
Can I combine two tracks?
No. This workflow selects one track for processing; it is not a multitrack mixer.