Raspbian doesn't have a default application for playing audio/mp3 files, so I went into the File Manager PCManFM, found the mp3 file, right click > Open With > "Custom Command Line" tab > Command Line to Execute > typed: omxplayer %f > Application Name > OMXPlayer
Unfortunately I did this twice, the first time with a typo, and both times put in OMXPlayer. Now when I right click the file there are two options to open with OMXPlayer.
Also, are there any audio players you would suggest? omxplayer doesn't appear to have a gui when I launch the file this way, so I have to go through task manager to kill it.
I had the same problem. I solved it by removing the custom command file in folder ~/.local/share/applications and updating the mimeapps.list file in the same folder.