In the Groove Cheats - PlayStation

Unlock All Songs
At the title menu, press: [Up], [Right], [Up], [Right], [Left], [Down], [Left], [Down], [Up], [Right], [Down], [Left], [Up], [Left], [Down], [Right].

Extras
Complete the indicated number of songs to unlock the corresponding extra:

Disconnected -Hyper song: 10 songs
Bounce marathon: 20 songs
Tell song: 30 songs
Bumpy modifier: 40 songs
Anubis song: 50 songs
Outer World marathon: 60 songs
Bubble Dancer song: 70 songs
Beat modifier: 80 songs
Disconnected -Mobius song: 90 songs
Liquid Moon song (In The Groove 2): 100 songs
Don't Promise Me ~Happiness Comes Mix~ song: 110 songs
Funk Factory song (In The Groove 2): 120 songs
DJ Party song: 130 songs
Tribal Style song (In The Groove 2): 140 songs
Infection song: 150 songs
The Legend marathon: 160 songs
Pandemonium song: 170 songs
Incognito song (In The Groove 2): 180 songs
Xuxa song: 190 songs
Wake Up song (In The Groove 2): 200 songs

Avoid being locked into a song by Chance
Normally, when you pick Chance, you are locked into the song it chooses. However, if you select the song and enter the settings menu, then back out with Triangle, you are returned to the song wheel and are no longer locked into the song chosen by Chance.