I don't get how people are having trouble with this, I'm using the A and D keys and I FC'd the one song in this game, then did it again, beating my previous score. It's not difficult by any means, and I'm a guy with essential tremors in my hands so I'm twitchy. Just play it and stop giving up if you fail once, you'll get better.
If it'd be the case that I only did it once, and not, a dozen times, then attempt to adjust the settings, and a dozen more times. I get it "get good" but with 1 difficulty setting that just leads to a repetitive losing experience that I don't even know if I'll be rewarded for getting through the off-beat song (that's difficult to get on-beat), beyond an ending that's potentially programmed in that's more than a "good job".
I want to enjoy this game. and games like this
So good job for getting through if you did. All I'm hoping for from this is more games like this that I can enjoy, and to give my honest feedback on the experience to help the creator if they read it, beyond just a simple hate message.