Quite an original concept to mix pong with a rhytm game, i like the idea of the obstacles so that you have to think bebore going closer to the net as the ball can go through but not you, its also cool that you can have the ball make a perfectly flat side bounce to take a bit of time and decide which angle you can bounce it back to. The art looks pretty good, the music is cool, and i definitively heard that hidden reference in there XD
I think people already mentioned it but, a visual help to catch the rhytm could be a nice complement to help the player synch up.
The only issue i had, isn't really with the game itself but a tiny bug in one of your menu screen just so you know its there, when you go on the more info screen there's no button to go back to the main menu :p
Other than this small thing i had no particular issue with the game, its a solid experience, i could only test the singleplayer so i can't really give any feedback about the multi sorry :(
Anyway, good job :)