Cullum paid homage to his hip-hop roots on his 2004 album, "Twentysomething," offering a rendition of the Pharrell Williams/Jay-Z track "Frontin.'" On his 2005 effort "Catching Tales," he took a mellower detour, tackling Doves' "Catch the Sun."

In a recent interview, Cullum said it does not feel awkward to cover the songs of a peer, as opposed to the jazz standards that dominate his albums.

"A lot of times when I'm asked that question, people look at it in a pop perspective--like Justin Timberlake doing a Linkin Park song. I look at it from more of a jazz musician's kind of angle," Cullum said.

"When Charlie Parker did songs, they were hits on the radio at that point. I want to use my knowledge of jazz harmonies and jazz music and reinvent it," he added.

Part of that experiment called for working with the Gorillaz's Dan the Automator on the "Catching Tales" track "Get Your Way," which blends cascading piano with a funky backbeat. The two met during the 2005 South by Southwest music festival in Austin, TX.

"It was incredible working with him. I met Dan when I was at South by Southwest. We were chatting. We had a drink. We had something to eat. He said, 'Why don't you come and be on my record?' I did that. So I said, 'Why don't you come and be on my record?' So he did that. That's how it works really," Cullum said.

Besides the Doves' song, Cullum also recorded versions of "I Only Have Eyes for You" and "I'm Glad There is You," along with originals including "London Skies," "Photograph" and "7 Days to Change Your Life." He said he does not chose the covers--hey chose him.

"Really you sit around and you play stuff, and sometimes things just jump out at you and say, 'You're going to play this,'" he said.