The Karmin i'm talking about is a duo from Boston, composed of Amy and Nick. You've probably heard of them by now or seen their videos up on a friends wall or through a tweet. They are mastering covers of Chris Brown and Weezy in the most interesting way ever. Changing the words to suit a female cover and adding in their own interpretations. Nick is in charge of the keys and some supportive vocals but does a good job transferring everything to the simplicity of a piano. Check out their two covers below as well as their youtube/twitter channel. Also, if you haven't seen the LOok At Me Now video you gotta check it out, it's pretty legit.
ps. there's a Katy Perry cover also! $$$ pss. Ke$ha cover is sooo silly and way better than the original, sorry boogs haha.