Oh, that's nothing new...sampling other songs. It's a bit different than two "modern pop songs" (released around the same time, I'm assuming, as I've not heard Kesha) sounding the same. A LOT of music these days sounds the same. Express Yourself was released a long time ago, wee one, maybe before you were born. Besides, I read Madonna thinks it's just fine.
There is nothing new under the sun.
Now, if you'll excuse me, I'm going to go compliment the shit out of Aretha Franklin and do RESPECT with all new words...then I be rich and stuff.
