PSP coder plum has released version 2.0 of his nifty homebrewed app, MP3PlayerPlugin.

Changelogs:

• version 2.0
  • Added menu item to change the clock
    • Change the clock applied to the surface patch, except this plug-in
      • Changing the clock is turned off so that the
  • Homebrew (EBOOT) Fix garbled
  • Operation and adjustment of other
• version 1.9 fix 2:
  • sceKernelLoadExecVSHWithApitype patch to fix a bug in the function part
• version 1.9 fix:
  • MUTE function back to the original
  • Operation and adjustment of other
  • Hiraku Kimi source

The app, which is basically an updated version of the old music.prx plugin, but with some added new features lets you play music while you're on the PSP XMB.