mp3.md

convert to variable bitrate mp3

ffmpeg -i inputfile.m4a -c:a libmp3lame -ac 2 -q:a 2 outputfile.mp3

constant bit rate

ffmpeg -i inputfile.m4a -c:a libmp3lame -ac 2 -b:a 190k outputfile.mp3

Loop and convert to lower quality

for f in .mp3; do ffmpeg -i "$f" -codec:a libmp3lame -qscale:a 5 "encoded/${f%.}.mp3"; done