To achieve the top score in a song you need to get all 'Perfect+' beats AND hold all the hold beats until the end.
Get Perfect+ by tapping exactly at the time the beat overlaps with the perfect bar area. If you’re a little early/late it registers as perfect only.
Unlock medals by getting high scores in your songs:
|Stars and Medals||Normal Song Point Threshold||Hard Song Point Threshold||Extreme Song Point Threshold|