After walking on stage to no fanfare beyond the dimming of the house lights at the Southern Theatre, Columbus, Béla Fleck and Chris Thile dove headlong into a five-minute, instrumental duel that caused the audience to fall silent and listen intently.

This changed immediately when Thile unexpectedly began singing the words to “Midnight Rider,” thus paying tribute to Gregg Allman, who had died the day before at age 69. It was just one verse and much of it was inaudible as the sold-out house at Columbus’ Southern Theatre roared its approval; there was no additional mention of Allman, just this appropriate homage to start out what turned into a more than two-hour performance from the world’s premier banjo (Fleck) and mandolin (Thile) players.

Their acoustic instruments were unamplified, save for mics aimed at each one, giving the music a purity of sound not often heard in live performance. Lighting was practically nonexistent, but for white spots and blue and yellow hues that lingered in the Southern’s gold arch that frames the stage.

And when an ethereal murmur leaked into Thile’s vocal mic early in the evening, he simply chuckled and told the audience to pretend it was organic as he and Fleck put on a clinic on how to pack a lot of notes into a small space.

That Fleck and Thile are virtuosos on their respective instruments is a given. At times the players went way out there and flirted with free jazz, such as on the unrecorded original “The Ghosts of Industry.” This is likely why Thile, when the pair returned for an encore at the end of the 75-minute follow-up, acknowledged the audience had just heard “a lot of mandolin-and-banjo music,” thanked them for listening and told concertgoers they were free to leave as he launched into a playful, sing-along rendition of “The Song that Never Ends” accompanied by laughter and clapping.

No one left. This was a performance to experience in the moment; a live recording wouldn’t be satisfying.

There was lots of humor spliced into the serious musicianship. Early in the second set, Fleck tore up the setlist to Thile’s mock horror; later, the banjo player asked what happened to the setlist. The pair played “Comey’s Waltz,” a real laugher Thile wrote for “A Prairie Home Companion” a couple of weeks back, that, like the opener, was difficult to hear for the crowd’s reaction – this time uproarious laughter.

Dressed in black and seated for the entire performance, Fleck alternated between two five-string banjos and engaged in occasional between-song banter on a mic he kept on a table behind him. Thile, in jeans and a light shirt, was more animated. He remained standing, his body jerking and heaving like a marionette as the music literally moved him. He sang lead vocals and was the gregarious host of the evening, which included a world-premiere number to start the second set as Thile joshed that the song was a freebie and that the customers would still get what they paid for with their ticket purchases.

From a 17th-century Scarlatti sonata to a rendition of Bill Monroe’s “Footprints in the Snow,” to numbers from Fleck’s Bluegrass Revival and the Flecktones and Thile’s Punch Brothers, not to mention the Allman Brothers Band, these extraordinary players put on a musical-history class. Like any lesson worth receiving, it wasn’t all fun and games and was a challenging listen at points. But learning is what makes education – musical and otherwise – so worthwhile in the first place.