This has been confirmed by me but I would like to add that you need the latest version of the PS2 Reality media player. I had the first beta release 1.0 but now there is a beta version 1.25. It wouldn't work on the first release. You can also put your mp3's on a seperate disc and swap it after you do the L1, L2, R2, R1 code at the main menu.
I have gotten all the divx movies I have to play successfully and now my mp3 discs. What a great little program. Now us guys that want to keep our Messiah 2's and not get the DMS3 have a way to play mp3s. You can get the newest version of the media player
here.