Significant plot details follow.
Note that R48, R49 and R50 are not unlocked during the course of the story and are unlocked by completing side quests.
- R48 is unlocked by completing the Master Instrument.
- R49 is unlocked by collecting all of the Phantom Notes.
- R50 is unlocked by getting an A Rank on all Rhythm Games on normal difficulty.
Please note that if you successfully get an A on a game and it does not update, it is not a glitch. The rank only updates if the score obtained was higher than before.
Also note that you only need to get an A rank once on a song in order for it to count toward unlocking Family Ties. Even if your A rank is not recorded because it is a lower score than another rank, the game will still count it.