Batch Mux with ffmpeg

[hbelouf]

I would like to know if there is a way to batch mux files with ffmpeg. I know how to batch convert video files using ffmpeg, by

for %%a in ("*.avi") do ffmpeg -i "%%a" -video_parameters "%%~na.mp4"

which correctly converts multiple files.

I need to mux several audio files, basiclly 2 audio files into one audio file, and that process repeated several times.
I know it can be done, but need help in getting this done.

Thanks.

[pcspeak]

Not sure exactly what you wish to do. Need more info.
2 audio tracks, different languages.
Just audio muxed or added to an mp4 (avi, mkv, etc.)

overlay the same track. Not sure why.
for %%a in ("*.mp3") do ffmpeg -i "%%a" -i "%%a" "%%~na-new.mp3"