[slyn]

It’s been ages so I don’t recall the exact details but you could pull a similar trick with the PS2 version of Guitar Hero to play custom songs on an unmodded console. You would burn a copy of the game with custom songs, insert and start a legit copy of the game, and then physically pull open the DVD tray and quickly replace the legit copy with the burned DVD at a specific time between when the PS2 had authenticated the disc as legit but before the game had actually loaded. It was a little finicky but with some practice it would work like 2/3rds of the time.

[kipchak]

You could use a similar method to play burned PS2 disks using a Datel (of Action Replay fame) "Swap Magic" disc and a card to pull the tray out. the Swap disk appeared as a genuine PS2 disk with bad sectors, which would cause the drive motor to stop and give some time for the swap to occur.