Many enjoy listening to their own music while playing games, but it’s a feature not available for PSP. Fortunately for us, Cpasjuste has ported the Music PRX plugin to support 3.90+ M33.
Note: “This has been tested on a 3.90 M33-3 slim PSP, WITHOUT the fatmsmod patch applied.”
Download from My Dedibox

Update: v2.2 is now available for download.
v2.2 Changes:

The Time Machine reboot function should now be fixed … stupid error i made. Note that the function is only made for use with NAND firmware and 150_340 one, with the TM files provided in this archive. If you want to use it with another firmware than 150_340, […]