Collect the indicated amount of Rhythpo to unlock the corresponding song for the Encore section of the Challenge series.

Dancing Mad from Final Fantasy 6 (BMS): 10,000 PTS.
Nakama wo Motomete from Final Fantasy 6 (FMS): 20,000 PTS.
Senkou from Final Fantasy 13 (BMS): 15,000 PTS.
Those Who Fight from Final Fantasy 7 (BMS): 25,000 PTS.