Two heavyweights of rap and R&B are teaming up for a joint album and tour.

Rapper Jay-Z and singer R. Kelly, both Grammy winners and multiplatinum artists, have collaborated on the disc The Best of Both Worlds, which is scheduled for release March 26.

They announced the project Thursday at a grandiose, rambling news conference at The Waldorf-Astoria hotel that featured introductions by Johnnie Cochran Jr. and testimonials from Sean "P. Diddy" Combs and Ronald Isley of the Isley Brothers. Members of their entourages sat nearby, dressed in fur and sipping Cristal from gold-encrusted goblets.

R. Kelly is best known for inspirational hits like "I Believe I Can Fly," but also raunchier songs such as the recent hit "Feelin' On Yo Booty." Jay-Z's hits include "Girls, Girls, Girls" and "Izzo (H.O.V.A.)."

They've previously collaborated on two hits: R. Kelly's "Fiesta" remix and Jay-Z's "Not Guilty."

"It's like mad scientists in the basement," R. Kelly said. "Jay is real creative, I'm real creative, and you want to get together and mix potions."

Jay-Z is on Def Jam Records while R. Kelly is on Jive. Def Jam will promote the disc in the United States and Canada, while Jive will do so in the rest of the world. While R&B and rap stars frequently do guest spots on each other's records such as Jennifer Lopez and Ja Rule, and City High and Eve a joint album is rare.

The first single is the sexually explicit "Honey," which played at the news event as Combs, Cochran and others bobbed their heads to the beat. When a reporter asked what the album's message would be for young people, R. Kelly said: "This album is not Disneyland. ... It's up to the parents to bring the kids up the way they should."

Besides the album and upcoming tour, the two also announced they would headline an all-star Urban Aid concert for LifeBeat to raise funds for AIDS charities. The April 9 event will air live on BET from New York's Beacon Theater, representatives said.