Comment by zzzeek

sure here's a command that a program I wrote to record my practicing and produce different mixes uses

    /usr/bin/ffmpeg -i "/path/to/musicfile.mp3" -i "/path/to/covertune.mp3" \
       -filter_complex [1:a]volume=1[track1];[0a][track1]amix=normalize=false[output] \
       -map [output] -b:a 192k -metadata title=15:17:01 -metadata "artist=Me, 2025" \
       -metadata album=2025-12-23 "/path/to/file.mix.mp3"

chance of my coming up with that without deep poring over docs and tons of trial and error, or using claude (which is pretty much what I do nowadays): zero