An hour and a half of atonal vibraphone music is about as esoteric a niche as music gets, unless it’s an hour and a half of atonal vibraphone music without an intermission. In this case, the music was almost secondary to the event, the first concert of a five-day festival of vibraphone music by Stuart Saunders Smith, which opened Wednesday night at Linehan Hall. Saunders Smith, who passed away in 2024, was a longtime faculty member of University of Maryland, Baltimore County.