Thank you for the great review. Wer are currently working on v1.1 to make the 2-player-mode even more fun (we removed the knockout feature so both players can do really bad and can still finish the song).
The high scores are being saved to the cartridge (.crt) but you need some extra steps on C64 Ultimate or VICE before you remove the image to save the current image back to disk. Just google "easyflash high score saving".