They play the violin, and sit on stage immediately to the conductor’s left. They initiate the orchestra’s tuning and sometimes play solos. They command large salaries. For many casual concert-goers, or even habitual ones, that may be all they know about this rarest of orchestral species: the concertmaster. And for the public at large, the term may simply draw a blank stare, or be filed away in a well-stuffed folder labeled “decorous conventions of an art form cloaked in mystery.” (Video courtesy of Boston Symphony Orchestra)