I tried to figure out how to combine/sync the two casette, but couldn't. I had the 2 types of the same color, had the rewind button clickable, but nothing happened. What did I miss? Nice artwork, and great concept by the way!
You actually have to click and hold the Rewind button until the music synchronizes and merges the cassettes.
I will add more explanations on the Game's page. Sorry I didn't make the instructions on the gameplay clear.