The first thing that grabbed the audience’s attention Sunday after series director Geoff Nuttall sauntered blithely out onto the stage was … his sudden lack of hair. Nuttall has a thing for weird hair (he dyed it blond the year he took over the series). Thus far this festival, he has been sporting shoulder-length hair in its natural color: medium brown (I think). But apparently, both he and his wife got tired of it; so he, Tony Manzo, and Pedja Muzijevic got together Saturday evening and gave each other buzz-cuts with a set of electric clippers. Manzo and Muzijevic didn’t have a whole lot of hair to begin with, so when they appeared later, they didn’t look appreciably different. But Nuttall did. Don’t get me wrong, Geoff: not bad, just different!

This program kicked off with something a bit different: the Sonata for Violin and Piano by Leos Janacek. Music by this most eclectic of late romantic-era Czech composers often strikes people as a little strange, with quirky rhythms that are often hard to follow, really different sorts harmonic schemes and unpredictable dynamics. Nuttall called it all “crazy.” But most people will find that Janacek’s music, while distinctly modern-sounding, will grow on them. Knowing what’s behind his tricks helps: for example, his habit of modeling his rhythms after human speech patterns. Of course, it helps if you speak Czech, but just learning that fact is a real eureka moment for many listeners who are trying to figure him out.

Janacek started out writing music in the style of his compatriots, like Smetana and Dvořák, and this violin sonata started out as an early work that he just couldn’t seem to finish. But as he was approaching old age, his new style (and his most productive period) kicked in; he returned to the piece in 1914, finishing it in the compositional voice that we now know him by. Enter violinist Jennifer Frautschi and pianist Stephen Prutsman, in his first series appearance. His flowing shoulder-length hair made up for Geoff’s lack of it.

The music was typical for Janacek: abrupt rhythmic and dynamic shifts on top of hairpin harmonic turns; moments of brutal power and brusque surprise alternated with moments of sweetly beguiling lyricism. The crowd seemed to get into it, or so their enthusiastic applause told us.