Dr Dre's Detox ghostwritten by Ludacris?

The latest track to leak from the hotly anticipated Dr Dre album was written and performed for him by rapper Ludacris

Original G? ... Dr Dre drafts in Ludacris to write his rhymes. Photograph: Corbis

Since the release of Eminem's Relapse, Dr Dre's Detox is the now most anticipated album in hip-hop. It's just a pity he doesn't seem to be writing his own raps.

Starting out as a member of NWA, Dre is now primarily a producer for hip-hop heavyweights including Snoop Dogg, Eminem and 50 Cent. His work production is exemplary, but he has also strived to prove his lyrical credentials over the years. On The Chronic, released in 1992, Dre raps with Snoop, Warren G and others. The same was expected for Detox, now five years in the making.

But as Detox's latest leak arrives on the internet, what emerges is that it is not Dre rapping. It is Ludacris. In Dr Dre's voice.

"With 30 mil sold, where's the fucking gratitude," Ludacris raps on OG's Theme. "I'm much more than 6-4's / Gun talk, weed smoke and sick hoes / That's why most of them have come and went / I just recoup, recreate and reinvent."

Ludacris does a surprisingly good impression of Dre. Of course, he's being paid to – this is clearly a "reference track" for Detox, where Dre will re-record Ludacris's lyrics. Ludacris confirmed this explanation on Twitter. "It was fun trying [to sound like Dre]," he said.

"Ain't no nigga better than Doc Dre," Ludacris spits on the song. Perhaps he ought not be so modest.

• This article was amended on 15 July 2009. The original said that this was Detox's first leaked track, and implied that the ghostwriting involved was unusual (rather than with precedent). This has been corrected.