Unlock All Songs:
At the title menu, press
ps2_up.gif ps2_right.gif ps2_up.gif ps2_right.gif ps2_left.gif ps2_down.gif ps2_left.gif ps2_down.gif ps2_up.gif ps2_right.gif ps2_down.gif ps2_left.gif ps2_up.gif ps2_left.gif ps2_down.gif ps2_right.gif

Unlock 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