"For 25 years I've been playing American classical music, broadening the tent of what's perceived as American classical music," O'Connor says. A question for this audience: "Four hundred years ago the violin was made and perfected, the scroll and tuning pegs, the neck and fingerboard, the ribbing, the contoured and graduated top and back, producing the acoustic principles required." This "unusual contraption," he says, "mechanical device, really, has never been improved upon in four hundred years." He's playing a new violin, made by a great maker right here in Maine -- Jonathan Cooper -- and he thought he would ask this audience if there's another contraption like the violin/viola/cello/bass, invented that long ago and not yet improved-upon. (Someone shouts out: the wheel! Someone else: ice cream!)

Another interesting thing about the violin, O'Connor tells us, is that it's been a cornerstone of American music for 400 years. He's developed a violin method book, which will be coming out in a couple of weeks, which utilizes American tunes to teach how to play the violin. The concept's been around in fiddle circles for a while. The book will use America, Canadian, and Mexican tunes as well, and looking at cultural relevance to help aid the lessons. His hope is for young people to fall in love with the violin in new ways.

He gives a couple of examples of why string playing is so important in American music. Bluegrass music and western swing were both invented in the 1930s and 40s, developed from earlier Appalachian styles. He features a lot of those old traditional terms in the book, and is interested in how this material can develop a new kind of classical string playing and broaden the tent of classical music in America.

First example: the Florida blues, from about 100 years ago. It's syncopated and familiar. Then an excerpt of something created from the blues but featuring newer techniques: twice as sultry, with a kind of come-hither virtuosity. Then we get a taste of ragtime, fast and danceable, and a short snippet of a jig and to show how that developed into American classical music, an excerpt from his fiddle concerto, which is equally fast and charming. "These are some of the ways that American music develops and continues to develop," O'Connor says.

He cites parallels between American folk music and European classical music; both genres have existed fr 400 years with very little overlap. A rare exception to that is Copeland's hoedown, of which he plays us a little bit. (You can hear it in this YouTube video.) It's a catchy tune but fiddlers almost never play it. A tape was recently rediscovered: four years before Copeland wrote his "Rodeo" in 1941, a fiddler played that tune with those exact notes on tape for the Library of Congress. "When I discovered there was an original recording, I asked a friend of mine, did the fiddler compose and play it in standard tuning? It turned out he'd retuned his fiddle," and that was not passed along in the orchestral setting -- so O'Connor plays it for us on a re-tuned fiddle.

The phrases sing, as he promised -- it pours out of the fiddle with such effervescence that one might imagine it was effortless, and we all whoop in applause. "This is one of the things I thought I'd try to bring to the forefront," O'Connor says, "appreciation of traditional materials used in new settings." This (re)discovery of folk music is a big piece of his method.

O'Connor also offers string camps -- music training for kids -- where classical training can coexist alongside jazz and world music all taught on violin. (Here's an article about those camps; he tells us that more than 7,000 students have been trained in this way.) He and a student collaborate to play "Appalachia Waltz," music which exists in the space between classical and American folk music. O'Connor has recorded it with Yo-Yo Ma (read more aout that collaboration here.) The student who joins him is Ruby Jane Smith (Pop!Tech bio; website) -- aged fourteen.

The two fiddle voices intertwine in a gentle duet full of close harmonies, seconds resolving into thirds, and the waltz's characteristic heartstring-tugging melancholy. Sometimes faster, sometimes slower, the tempo changes organically. When I crane my neck to peer down from the opera box where we're liveblogging today, I see the two musicians so intent on their fiddles and the notes they're creating that it's as though the opera house full of audience wasn't even here.

"If you feel, like me, that there could be a reimagined America with more music-making, playing string music that could be perhaps more culturally relevant to the Americas, let me know," O'Connor says.

And Ruby adds that she's honored to be here at Pop!Tech, that being here has been life-changing for her. "You hear people talk about changing the world all the time, but to be here and be listening to people who really are changing the world is really inspiring." She first came to Mark's camp when she was ten; she'd been playing fiddle since she was two. She remembers the first time Mark showed up, midway through the week -- "it was like Elvis Presley walked into the room, but ten times better than that!" Performing by his side is clearly an emotional experience for her, and the audience applauds.

They wrap up with an old fiddle tune transformed into a classical duet, "another demonstration of how classical music and American fiddle can meet." This one's a toe-tapper, fast and swirly and upbeat and danceable. What a treat.