Rapper Wiz Khalifa is helping to give Miley Cyrus and Britney Spears' new albums a hip-hop flavour after recording songs for both pop stars for free. The Black and Yellow hitmaker has been hitting the studio for a variety of new projects and reveals he's contributed guest verses to the two singers' highly-anticipated comeback releases. He tells America's Sister 2 Sister magazine, "I'm recording, I'm doing a lot of features... I did a song with Miley Cyrus. I'm on Britney Spears' album... I'm doing a lot of different stuff in the studio." And Khalifa offered up his services for free - because he only works with musicians he's fans of: "A lot of artists, they do make their money off of features, but I don't really charge people for features because if I do a song with you, that means I f**k with you (I'm a fan) and I see some good coming from the project, so I don't really have to get paid up front. You get royalties on your song when the song sells."