Nas is the latest rapper to record a track for Dr Dre's forthcoming studio album, Detox.
The album, which will be Dr Dre's first new album release since 2001, will also feature Eminem, 50 Cent, R Kelly and possibly Busta Rhymes, Snoop Dogg, The Game and even Jay-Z.
Speaking to Billboard about his collaboration, Nas said: "I did a joint, I think it's crazy."
Nas added that he wants to work with Dre on a full album at some point, describing Dre as "the best producer of all time".
Back in 2007, 50 Cent said of Detox: "He's working on it. I've recorded two songs for him. Dre's such a perfectionist. But sometimes that can be a bad thing. You create new pressure when you wait that long.
"When you put a new album against the last two classics, people will scrutinize it if they become impatient."
In an interview with Loud.com, DJ Quik revealed that Dr Dre has recorded around 400 songs for the album, and he himself had heard about 60 of them. Dre has recently been getting piano lessons from Burt Bacharach - true! - and, according to Quik, has been reinterpreting "symphony stuff" by Frederic Chopin.
Dre has been working on Detox in some capacity since 2000, making it the 'Chinese Democracy' of hip-hop.
However, Detox will not emerge until Dre has completed work on Eminem's forthcoming album Relapse.