It's unclear whether you have to mimick the rhythm since you can just continue pressing the correct buttons no matter how fast or slow you press them.
The visual aid becomes nearly invisible at the later stages of the game. I don't know if it's intentional or not, but currently it's quite frustrating.
It's unclear if you can lose or not. When you press the wrong button, it seems to simply repeat, no matter how many mistakes you make.
I'd suggest adding one more instrument for variety. Also make it so you have to remember smaller series of notes instead of really long ones. That way, the player has less downtime between the game telling the player what to play and the player having to imitate the rhythm. Maybe the speed then could slowly increase over time to increase difficulty.