has confirmed that it is possible for the PS3 to play songs from the hard drive while a game is in play. This Spanish gamer was playing 'Everyday Together' on the PS3 (a Japanese downloadable PSN title) and he was trying to guess what each option did and stumbled across an option that asked him which tracked he wanted to play.
Moreover, the options were actually from there on in Spanish (his firmware language) which indicates that the player is integrated into the firmware and not options of the game as it is Japanese. Further to this, the player is quite advanced and it is clear Sony has been working on it as it has a number of options such as random playback, repeat a folder and related options.
But that is not all, this game allows you to send IN-GAME messages to your friends so you don't have to quit the game. It is also believed that this title is actually the first to take advantage of Remote Play with LAIR actually being the second.
Although it may be the first retail title to utilize XMB access, these functions have been in the PS3 early on as Sony leaves it to game developers to use them. Also, without the ability to change game files an exploit doesn't appear likely.