Dec. 20 Night of Music w/ Claran Nagle and Tara Novak Bemis Center, 724 S. 12th St. 7 p.m., $7/$5 members 341.7130, bemiscenter.org Musical collaborations can spring from unexpected sources. Irish tenor Claran Nagle is rooted in the traditions of his native Old Sod. He trained at prestigious schools there, he performed with the National Chamber Choir of Ireland and Opera Ireland and he was Riverdance’s male lead singer. Violinist-composer-vocalist Tara Novak, originally from Omaha and now dividing her time between New York City and Ireland, boasts a repertoire of classical, jazz, rock, pop, Broadway show tunes, experimental theater music and traditional Celtic sounds. She is lead violinist for Three Irish Tenors and Druid, two touring ensembles founded by Nagle that feature her compositions. She performs on an acoustic violin and a five-string, metallic blue Violectra. The pair head the Celtic Rock group Ishna, a melding of classical, Irish and rock.