Stjepan Hauser, from Croatia, and Luka Sulić, from Slovenia, are both classically trained and form the band 2Cellos, which has sold out shows in Portland, Seattle, Denver, Boston and New York.

When Stjepan Hauser and Luka Sulic began studying cello as youths in Croatia, they had no idea they’d be recording rock ‘n’ roll classics, playing to sold-out arenas, collaborating with the ...