Thanks for the input.
I got the 30lines per Level thing from Tetris effects, which worked there quite well. But i guess due to the new mechanic making the game slightly slower than regular Tetris, thus making the 30 lines per Level feel more like 60. I guess i could shorten it (at least for the first few levels) to 10 rows. And maybe make the first few levels a tiny bit faster.
But there is music. Can you check again if there is music on your end and you didn't accidentally disable it?