PSP homebrew developer TotalNoob has released an application that, at first may seem tiny and simple, but is actually still quite useful in its own right. MusicHold allows you to activate the shoulder buttons and Volume buttons of the PSP, even if it's on hold mode.

Changelog for MusicHold v0.1:

* If you press HOME and START in hold modus, then will enabled the L,R,Vol+ and Vol- buttons