The wild success of the "O Brother, Where Art Thou?" soundtrack was one of the most unexpected musical phenomena in recent years. A wide spectrum of fans has bought this collection of bluegrass, folk, gospel, blues and old-time music.

For many listeners, this album opened a door into the world of roots music. After opening that door, some fans timidly halted their journey, unsure where to go next. These folks said to themselves, "I love this album, and I wonder where can I find more music that's just as satisfying. What CDs should I buy next?"

Below are some suggestions to answer that question. Whether youÕre a veteran of the bluegrass festival circuit or a newcomer who's just beginning to explore Americana music, there's something here that will strike your fancy.

The concert documentary "Down from the Mountain" was filmed in May 2000, months before the "O Brother" movie or soundtrack was released. The concert featured an all-star lineup of musicians who also appear on the O Brother disc, including the Cox Family, Alison Krauss, Gillian Welch, and the Whites. The soundtrack to this concert film is simply one of the best live albums ever made.

The Down from the Mountain soundtrack has sold over 500,000 discs – which is nothing compared to the staggering 7 million copies of O Brother that have flown off shelves – but this disc is just as amazing, and more musically cohesive, than its big "brother." The film is also available on DVD, giving the viewer a front-row seat to a truly historic concert event.

Most of the O Brother participants are industry veterans, and none has a deeper catalog than Ralph Stanley, who has recorded over 180 albums. Last year, he released a self-titled disc on DMZ/Columbia that will appeal to fans who loved his a cappella reading of "O Death" and yearn for similar material. Ralph's reputation was built on the influential recordings he made with his late brother, Carter. The Complete Columbia Stanley Brothers collects the duo's classic cuts from 1949-1952.

Alison Krauss & Union Station's recent double-CD Live is a flawless portrait of the best working band in bluegrass today, and it features Dan "Soggy Bottom Boy" Tyminski singing "I Am a Man of Constant Sorrow." Guitarist Chris Thomas King, who portrayed a Delta bluesman in the "O Brother" movie, used this film role as the inspiration for his mesmerizing blues album The Legend of Tommy Johnson.

One group that popularized old-time music long before O Brother is the Nitty Gritty Dirt Band. All three volumes of the Dirt Band's Will the Circle Be Unbroken series – released in 1972, 1989, and 2002 – feature legendary fiddler Vassar Clements, banjo deity Earl Scruggs, bluegrass pioneer Jimmy Martin, and a parade of like-minded musical guests. Each Circle disc is an indispensable delight.

Fans of contemporary acoustic music will also reap rewards from these fine albums: Patty Loveless, Mountain Soul; The Del McCoury Band, The Cold Hard Facts; Dolly Parton, The Grass Is Blue; Ricky Skaggs & Kentucky Thunder, History of the Future; and Rhonda Vincent, Back Home Again.

Adventurous listeners interested in the history of roots music should seek out the archival recordings in the Alan Lomax Collection on Rounder Records. There are dozens of CDs in this series, which preserves the field recordings that Lomax made during his extensive travels. The opening track on O Brother, "Po, Lazarus," is a 1959 recording of James Carter and other men who were incarcerated at Parchman Farm in Lambert, Miss. That track, along with additional recordings made at the segregated prison, can be found on Rounder's Southern Journey Volume 5: Bad Man Ballads.

Thanks to the diverse talents showcased on O Brother, many CD buyers are now discovering magnificent music that will stand the test of time. Happy hunting, and happy listening!