In what is rapidly becoming a hip-hop tradition, the soundtrack to "Caught Up" -- an urban crime movie -- has brought together a collaborative all-star lineup.

Rap heavyweights KRS-One, Snoop Doggy Dogg, Luniz, Mack 10 and Wu- Tangers Inspectah Deck and GZA all lent their luster to the project, which was recently released on CD by Noo Trybe Records.

Some of the artists that paired up for the "Caught Up" soundtrack were friends and comrades. Others were relative strangers. Bay Area rappers Luniz were all set to do a remix of the song "Just Mee & U" off their second album, Lunitik Muzik, as their contribution to the soundtrack. Then Luniz's Knumskull and Yukmouth thought to tap their pals Daz and Kurupt from the L.A.-based crew Tha Dogg Pound, and a collaboration was born.

"'My Buddy' (RealAudio excerpt) was supposed to be a remix [of 'Just Mee & U'], but we decided to do it with Tha Dogg Pound," said Knumskull, a.k.a. Gary Husbands, 24. "Instead of just calling them and having them do their part separate, we all sat down and wrote it. We knew them from before, so it was like family getting back. We all knew the basic theme of the song was 'my buddy,' and it was like Yukmouth and I are two people that was one. He's my buddy and friend. So we come together as four, to be one."

The situation was different for "Girl" (RealAudio excerpt), a song that Knumskull said is about the time that he and Yukmouth peddled drugs. ("We used women as a metaphor for drugs because women can take over your life just like dope do," Knumskull explained.)

Unlike the collaboration with their pals in Tha Dogg Pound, Luniz were working with a relatively unknown L.A.-based rapper, Crooked I, on "Girl." "The label hooked it up," Knumskull said. "We never even met him before."

New York rapper KRS-One worked with reggae performers Mad Lion and Shaggy for the uptempo track "Ey-Yo! (The Reggae Virus)" (RealAudio excerpt). It features Shaggy hollering "Ey- Yo" in an echo of new-wave rockers the Bangles' 1986 hit "Walk Like An Egyptian" and KRS-One adding his political and intellectual bent, with lyrics such as "Don't be a fan, like De Niro/ be a teacher/ be a role model/ be a hero."

Alexander Mejia, director of A&R for Noo Trybe Records, said each artist submitted a couple of songs for consideration to the promotion staff that selected the songs and tailored them to specific scenes in the movie, which has already left theaters since its release earlier this year.

"We knew this soundtrack was going to be hip-hop driven, so we got the very best in the biz involved," he said. "We wanted to have artists that people love to hear with collaborations that had not been done before, [ones that] we could market to make a successful project."