Baritone Quinn Kelsey has a gorgeous voice. It’s large and sonorous, with a distinctive, slightly throaty (aka husky) quality, and a top so beautiful at forte that it could melt the hardest heart. Such a fine instrument, allied to an energetic stage presence, recently made for a most endearing Marcello in San Francisco Opera’s first-cast La Bohème, and an unusually warm, beautiful contribution to Michael Tilson Thomas’ recent San Francisco Symphony performance of Mahler’s Symphony No. 8.