Untethered from amplifiers and aided only by waist- and head-high mics, the Del McCoury Band’s music stampeded freely though a sold-out Stuart’s Opera House while their high harmonies soared over the 395 ecstatic concertgoers lucky enough to attend the March 4 hoedown.

The quintet centers around the 76-year-old namesake singer/guitarist and his sons, Ronnie, on mandolin and vocals, and Rob, on banjo and vocals. Joined by bassist Alan Bartram and a fiddler who filled in seamlessly for Jason Carter, the group revisited Del’s ties to bluegrass pioneers such as Bill Monroe and rolled through more contemporary territory as they covered songs associated with the Grateful Dead and written by artists such as Richard Thompson, Larry Keel, the Lovin’ Spoonful and others.

With a thick shock of white hair and sporting a smart, grey suit, Del stood out from his dark-haired, dark-suited bandmates. But he never stood away from them as they bunched closely together and played in unison. Over the hour-and-45-minute performance, the egalitarian elder statesman graciously ceded occasional lead vocals to his sons and fellow musicians and gave them all plenty of room to solo ferociously on their unplugged instruments; at times, Rob and Ronnie’s hands looked like pale blurs as they frantically peeled off banjo and mandolin solos that were as tasteful as they were tenacious.

Del was playful with the audience, telling short stories, giggling at the shouted feedback he received and taking requests. The band were all smiles as they batted round-robin solos, occasionally gathering around a single microphone to harmonize beautifully on disparate songs such as the gospel “You Better Get on Your Knees and Pray” and the playful “Nashville Cats.”

Without being filtered through amplifiers, the instruments took on a supremely clean tone rarely heard in an in-concert setting, and the music had a clarity matched only by the vocals. More than 50 years into his career, Del on stage sounds like a smooth recording and though he joked he can’t reach certain high notes anymore, he managed to effortlessly climb way up the scale. When he sang in harmony with Ronnie, the words came with the gorgeousness that’s attainable only when kin join voices.

“Cold Rain and Snow” and “1952 Vincent Black Lightning” were audience requests, while the rapid-fire “Bluegrass Breakdown,” the sprightly “Traveling Teardrop Blues,” the spasmodic “Rawhide” and the lonesome sway of “Bluest Man in Town” and Hank Williams’ “You Win Again” appeared to have been jotted on a loose setlist that existed only in Del’s head. The band were constantly watching him and having short, off-mic consultations between songs as they prepared for what tune might be called next.

Enthusiastic applause, whoops and standing ovations followed most every song and the audience stomped their feet for more when the band suddenly stepped back from the mics, bowed and walked off stage. If the two-song encore had been extended to 10 numbers, it still wouldn’t have been enough.