EvoluTone by BumbleBirds 2012-09-18T00:11:00
There actually is a small amount of tutorialisation in the game, but I guess it wasn't totally clear?
In the first few rounds when the cell flashes there's also a glow around the corresponding key's icon. That's removed a few stages in. We figured by that point you'd have "got it" and the training wheels would come off.
The timing never actually changes, you have exactly the same window to react in regardless of the stage you're at.
Glad some of you enjoyed it anyway! :)