I transcoded a bunch of music videos downloaded for free from the iTunes Store to audio only .m4as in the Finder, following the hint at http://osxdaily.com/2012/01/16/convert-video-to-audio-mac-os-x-lion/. After adding the audio files to my iTunes library, they still show the video icon in the library list, and the media kind in the Get Info panel says “Music Video”, with no way to change it to just “Music” like other .m4a files. How can I force these files to be recognized as simple music files?
You should be able to use subler to do that. Just open the file, go to other settings and you can set the media kind to "normal".