“In 2005 Till Fellner, an Austrian pianist then rising quickly, canceled an appearance in the Mostly Mozart Festival at Lincoln Center because of illness. A cold? The flu? A sprained finger? This time the matter was not so simple. Mr. Fellner had developed tinnitus, an ear affliction that rendered him extremely uncomfortable.” His recovery from the career-threatening illness was relatively swift, but his experience points up the continual danger of hearing loss faced by professional musicians.