@mitu That's the funny thing. mpg123 IS part of BGM so uninstalling BGM uninstalls both (hence the loss of music completely) but uninstalling mgp123 by itself removed its config I suppose. I manually plugged the info back in and left BGM out this time around and finally got it working. Thank you for your reply.
Please do not post a support request without first reading and following the advice in https://retropie.org.uk/forum/topic/3/read-this-first