It's just as well that there were only about half enough people to fill Nashville's Belcourt Theater Thursday night (March 23) for the Bobby Osborne salute. They were the better half.

No curious passersby or loud frat boys here. No recent converts pulsating with indiscriminate zeal. No singalongers.

These were the seasoned few, the ones who knew the literature and lore of bluegrass music, who savored nuance above dazzle, who wouldn't have thought of shouting out requests for "Rocky Top" but appreciated the song when it inevitably came along for what it once meant to bluegrass. Mostly middle-aged and older, these folks came to the party with decades of pleasant memories to tap.

On hand to render that service were Osborne and his band, the Rocky Top X-Press, along with Alecia Nugent, former Shenandoah lead vocalist Marty Raybon, Claire Lynch, Larry Stephenson, the Grascals and Marty Stuart and his band, the Fabulous Superlatives.

Now that his younger brother, banjo innovator Sonny Osborne, has retired, Bobby has elected to soldier on as a soloist. The tribute show was organized to call attention to the release of his new album, Try a Little Kindness, on Rounder Records.

Born in Hyden, Ky., during the Depression, the Osborne Brothers made their mark in bluegrass through Bobby's incredibly high tenor vocals and fluid mandolin playing and Sonny's imperious, full-gallop banjo picking. They also introduced a reliance on vocal trios instead of a single lead voice. After separate and joint apprenticeships with other bands, the brothers stepped out on their own and quickly established their reputation as musical experimenters. (Unlike many bluegrass purists, they would eventually use drums, piano and steel guitars on their recordings.)

In 1958, they had their first and biggest chart single, "Once More." Two years later, during the folk music boom, they made history by becoming the first bluegrass act to play on a college campus (Antioch College in Yellow Springs, Ohio). Recording for Decca, they continued to chart with such fare as "Up This Hill and Down" and "Roll Muddy River."

Then, in 1968, they scored with the song that would become their signature, Boudleaux and Felice Bryant's irresistibly catchy "Rocky Top." Although it reached only No. 33 on the country chart, it pinpointed the Osbornes' sound as surely as "Foggy Mountain Breakdown" had for Flatt & Scruggs. The brothers joined the Grand Ole Opry in 1964 and were inducted into the International Bluegrass Music Association's Hall of Honor in 1994.

Unlike many tributes, which feature artists chosen for their star power, this one was rich with performers who had been demonstrably influenced by Osborne Brothers music and who knew their canon intimately. Each act sang selections from the Osbornes' catalog, and each brought the guest of honor to the stage to join them in song.

Osborne opened the show with six picks from his current album: "It's Gonna Be Rainin' Til I Die," "West Virginia," "Mansions for Me," the instrumental "Rocky Top X-Press," "Sunday Morning Coming Down" and "The Hard Times." He noted that the Belcourt had once been the home of the Grand Ole Opry (1934-36) before the radio show settled in for years at the Ryman Auditorium.

"This is one of the best things that ever happened to me," Osborne said of the tribute. "It scares me to think about it." Wearing his trademark white planter's hat and sunglasses, the 74-year-old trailblazer sang his parts smoothly and effortlessly. His only apparent concession to age was posting the lyrics of "Sunday Morning Coming Down" on a music stand. "It has a lot of words in it," he said apologetically.

Nugent and her five-piece band came on next. Nugent also has a new album out on Rounder, A Little Girl ... A Big Four-Lane. She sang the forlorn "Listening to the Rain" and "Windy City" before inviting Osborne back out to accompany her on "Once More."

Next up was Raybon, who ambled out almost unnoticed until master of ceremonies Kyle Cantrell introduced him. He didn't need even that much fanfare. Standing alone and accompanying himself on guitar, he drew cheers from the crowd with the first sad notes of "Ghost in This House," a hit for Shenandoah in 1990. His voice was strong, charming and dramatic, and the crowd clearly loved hearing it.

Recalling that he began his career playing bluegrass with his family in Florida, Raybon said, "If it hadn't been for the Osborne Brothers, we wouldn't have had nothing to sing." He added that the Osbornes were to his generation what Flatt & Scruggs had been to the previous one.

To prove his point, Raybon beckoned Osborne and his band to the stage and lit into the hard-driving "Big Spike Hammer," an Osborne staple. They concluded the set with "Will You Be Lovin' Another Man."

Claire Lynch and her band made their entrance with "This Heart of Mine Can Never Say Goodbye." (Her new Rounder album is titled New Day.) Remarking that songwriter Paul Craft was in the audience, Lynch introduced his "Blue Heartache," noting that both the Osbornes and Gail Davies had recorded it. She brought Osborne back to sing the song with her, and they wrapped up with "Is This My Destiny."

Stephenson opened the second half of the show. One of bluegrass music's best vocalists, Stephenson began with "The Sound That Set My Soul on Fire," his tribute to the Osbornes. "When I heard that song, 'Rocky Top,' it changed my life," he said. Then he flipped his mandolin to show a portrait of Bobby Osborne on the back.

Waving Osborne to return, the 49-year-old Stephenson recalled that he was 14 when he first met Osborne at a festival in Culpepper, Va. "I said, 'I sing 'Rocky Top,' and he patted me on the head and said, 'If you like that, you'll like our new single, "Georgia Pineywoods." . . . He was nice to me, and there were those who weren't."

After this fond reminiscence, Stephenson and Osborne sang "Today I Started Loving You Again" and "Pain in My Heart," the latter being the first song Osborne ever wrote and one that Flatt & Scruggs recorded.

The Grascals next trooped into the spotlight and made their bow with the rousingly applauded "Hard Times." Two of the Grascals, bassist Terry Smith and guitarist-vocalist Terry Eldredge, are alumni of the Osborne Brothers' band. "They're such good teachers," lead vocalist Jamie Johnson said of the Osbornes. "They took bluegrass to a different level."

Osborne paired with the Grascals for "I'll Just Pretend" and then exited before they rocked the house with their final homage, "Roll Muddy River." Apart from Osborne himself, this Grammy-nominated Rounder recording group drew the loudest applause of the evening.

"In case anybody hasn't said it already," Marty Stuart said when he and the Fabulous Superlatives took the stage, "[Bobby] is one of the greatest voices to ever come out of this town." Aided by drummer-vocalist Harry Stinson, Stuart began his mini-set with "Up This Hill and Down," an Osbornes favorite from 1966, and followed it with the doleful "Makin' Plans."

Then, as the other musicians left the stage, Stuart invited Osborne to join him. "If you don't like this one," he announced to the crowd, "we'll give you your money back." With that, the two Opry icons -- Stuart on guitar and Osborne on mandolin -- swept into the majestic (and accusatory) hymn, "What Would You Give in Exchange for Your Soul."

When the hymn was over, Stuart walked off to let Osborne close the show. The honoree recalled that his final song had been released on Christmas Day of 1967.

"It's the greatest thing that ever came out in my lifetime," he said. As he spoke, all the acts returned to romp along with Osborne on an extended version of that long-ago Christmas present, "Rocky Top."

XM Satellite Radio recorded the show for Cantrell's program, Bluegrass Junction.

As the sound of "Rocky Top" faded away and the crowd applauded for an encore, not one in the audience shouted out for Osborne's bravura piece, the ear-splitting and breath-challenging "Ruby, Are You Mad." But everyone would have been happy to hear it.