About two-thirds of the way through the “Down from the Mountain” concert Tuesday at Kansas City’s Starlight Theatre, emcee Rodney Crowell asked the almost-full house, “Doesn’t it do your heart good to know this music is alive and well?”

Yes, Rodney, yes indeed.

Relying on the Grand Ole Opry’s practice of steering instrument-carrying performers around a stationary set of microphones, the 3 1/2-hour show quickly evolved into a breathtaking celebration of American roots music that mix of folk, country, gospel, blues and bluegrass that had the good fortune of finding its way onto the “O Brother, Where Art Thou?” movie soundtrack.

The weather was perfect, the sound system pristine, the audience hushed and respectful, providing a perfect setting for an ever-changing cast of singers, pickers, strummers, pluckers and no drummers. A few of the highlights:

Emmylou Harris, Alison Krauss, and Patty Loveless’ a cappella rendition of “Didn’t Leave Nobody but the Baby.”

Crowell’s joining Harris, Krauss and dobro master Jerry Douglas for a chilling version of Townes Van Zandt’s “Poncho and Lefty.”

Loveless and Nashville Bluegrass Band’s Stuart Duncan backing Ralph Stanley on a near-a cappella, mountain-style take on “I am a Man of Constant Sorrow.”

Ricky Skaggs leading his band, Kentucky Thunder, through the rousing “Black-eyed Susie, which included the line, “All I need to keep me happy/Is four kids to call me Pappy.”

The Whites’ three-song set, including a remake of Kitty Wells’ classic “Making Believe” and the Carter Family’s “Fair and Tender Ladies” and “Keep on the Sunny Side.”

Stanley, the tour’s unofficial headliner, closed the evening with a four-song set that included the stoic “O Death” and “Pretty Polly,” a generation-spanning duet with Loveless.

“He is the father of mountain soul,” she told the audience. Stanley, well-schooled in the art of understatement replied, “Patty, you’re mighty good, too.”