Dropchord is today's paid Android app that's available for free from Amazon.
This is a music game with two modes,. Standard and Full Mix. You have to collect notes to progress to the next track. You manipulate the line by holding the screen on each side of it, sliding it around.
The game is currently rated 2.6/5 from 18 reviews on Amazon. The biggest complaint with users is that they simply can't understand what you are actually supposed to do - and this is a definite problem. The game looks like it could be decent, or interesting, and it certainly seems reasonably polished, but figuring out how to play is difficult. Just saying collect notes and avoid scratches is not enough; how do you do these, and what are they.