Alastair Willis conducts the Lexington Philharmonic in its first rehearsal of Osvaldo Golijov's "Last Round," which requires violinists and violists to stand as opposing orchestras. LexGo photo by Rich Copley.

When Lexington Philharmonic Orchestra fans are settled into their seats Friday night, they’ll find that the musicians aren’t.

The violins and violas, at least, will be standing, poised to dance and maybe throw down a few punches — musically, that is — playing Osvaldo Golijov’s Last Round. The piece calls for the musicians that can to stand, and guest conductor Alastair Willis is too happy to follow that order.

“I’m all for that,” Willis said in an interview Tuesday afternoon. “Why have we always played in the form we always play in? Because it works. Because it’s how orchestras historically sound best, for most of the repertoire. No one’s ever going to change that, but I love to find the variety.”

Willis explained the variety presented in Last Round, which will open Friday’s concert.

“You’ve got two string orchestras set apart from each other,” Willis says. “There should be a gap down the middle, and straight in front of me are the basses, holding everyone together. It’s a wonderful visual. There’s a stereo effect of one idea bouncing across the stage from one orchestra to the other, and you have the concept of two tango dancers who are perhaps involved with each other, arms flailing, legs thrashing.”

Willis has had a chance to consult with Golijov through their work with Yo-Yo Ma’s Silk Road Ensemble and the Chicago Symphony Orchestra, where Willis has conducted and Golijov is composer in residence.

“His music just speaks to new audiences,” Willis says of Golijov. “It’s an incredible fusion of classical ideas with non-classical ideas — modern jazz, modern folk music — in the most original way.”

Also on the concert is Alberto Ginastera’s Harp Concerto and Ludwig Van Beethoven’s Symphony No. 6 (Pastoral) which will be played in traditional orchestra seating.