During an onstage interview halfway through a concert on Thursday night at the Miller Theater at Columbia University, the conductor Brad Lubman asked the composer Georg Friedrich Haas how he had become interested in writing microtonal music. It was a simple question that might have occurred to anyone in the hall. Mr. Haas’s works, some of which have become staples of the contemporary repertory, make striking use of sounds that lurk between the semitone steps of the conventional Western scale. Mr. Haas sidestepped a simple answer. Microtones exist, he said; why not use them? Anyway, it’s only a problem for the conductors and performers who have to interpret faithfully pieces like his latest opera, “Thomas,” in which Mr. Haas used some 1,600 different pitches. Pushed gently, he divulged some history, but he had a more important point to make: using microtones is not an end in itself, but a means by which to provoke strong emotional responses from his listeners.