a very common music files format is .rm files,
on linux, .rm files need special handling which not provided with 'ubuntu' by default (I don't know about other distros)
I've found 'RealPlayer' Music Player version for linux provided by Helix , and here, I'll guide you to Install it on Your Ubuntu Machine.
Installing RealPlayer :
1. Download (RealPlayer 11) from this page http://www.real.com/linux
it will download a .bin file (never mind)
2. After download, from bash, log in as system root (I prefer this way) and run the .bin file.
-> su - (optional but prefered)
> enter toor password
-> cd /home//Desktop
-> ./RealPlayer11GOLD.bin
3. then the installation will begin and ask you about the setup location,
I myself have installed it on /etc/Real , you can change the destination or make like me,
Note, Fedora and openSuse users can download the .rpm file from the same page
Hope I help someone
Sala
m