North America
Get four medals to unlock the telephone mini-game in "Rhythm Toys". Dial the following codes during the telephone mini-game to get a hidden song from Rhythm Tengoku on the Game Boy Advance. Note: The codes can be found at various hidden locations.

Dial 5553282338 (found in Business Card under "Rhythm Toys"; requires 1 medal).
Dial 5557325937 (found in Tunnel Endless; requires 12 medals).
Dial 5557268724 (found in Samurai Slice Endless; requires 17 medals).
Dial 5557625688 (found in Battle Of The Bands; unlocked by completing all 50 stages).

Japan
Get four medals to unlock the telephone mini-game in "Rhythm Toys". Dial the following codes during the telephone mini-game to get a hidden song from Rhythm Tengoku on the Game Boy Advance. Note: The codes can be found at various hidden locations.

Dial 831[Music Note]831[Music Note]831[Music Note] (found in Business Card under "Rhythm Toys"; requires 1 medal).
Dial 2[Music Note]21[Music Note]98 (found in Tunnel Endless; requires 12 medals).
Dial 246936[Music Note]1 (found in Samurai Endless; requires 17 medals).
Dial 44[Music Note]8231[Music Note] (found in Live Contest; unlocked by completing all 50 stages).