.msv is a Sony audio file type.
How can I play this file on 12.04?
Unfortunately, due to *.msv being proprietary in nature, it is extremely unlikely you'll find a way to actually play this file (unless Sony releases information on how to decode that file, which in itself is pretty unlikely).
Your best bet is to find a Windows machine that can convert the .msv into a .mp3, .wav, or *.ogg file and then playback the file in Ubuntu.
Just so you know, someone else documented their journey into playing a .msv file on Kubuntu. Maybe you could read that to see if you are prepared to do as the author did to get the audio from the *.msv
Did you try mplayer? I've read somewhere that it can play back these files.
Important note: I did not try it. Please try to use it to play the msv files and report the result for others to use!