Making a living as a solo violinist can be an awfully tough road in a music world obsessed with youth and crossover celebrity. So when the celebrated young violinist Jennifer Koh saw the odds against her, she decided to carve out a career niche that would set her apart from the crowd, “working with composers living and dead, getting into their heads and hearts through their scores, and developing personal relationships with those who are still alive, notably [Jennifer] Higdon and [John] Zorn.”