Homebrew dev plum released a new version of the Mp3PlayerPlugin Lite v1.4 for 5.00 M33, 5.03HEN, 5.50GEN, 6.20TN und 6.35 PRO!
With this plugin you're able to hear your own music in PSP games.
Controls (translated by me):MP3PlayerPlugin UPDATE v1.4:
plug-in music playback
Plug in the operation of the light, skip, add the blending mode menu
How can such changes in the expression of the specified channel mute
DownloadL + R + Left / Right = select other songs
2. L + R +  = Pause
3. L + R + O = Change the order of play (in order, randomly, etc.)
4. L + R + Triangle = Play the song again.
5. L + R + Up / Down = change in volume.