Cheat Mode
The following pushbutton codes will temporarily unlock said songs for one arcade mode / free mode session when entered on the title screen. The numbers correspond to the Pop'n controller's buttons from left to right. Knock Out Regrets (Punkish Girl) is permanently unlocked if you start the game with a DDR Str!ke save on your memory card. Jet World (Hard Country), and Cassandra (Ska) are permanently unlocked if you start the game with a Guitar Freaks / Drummania V save on your memory card.
38271619 - Unlock Jet World (Hard Country), and Cassandra (Ska)
97976868 - Unlock Knock out Regrets (Punkish Girl)