If you're looking for an intellectual challenge, here it is. Schnabel, who was renowned for his penetrating performances of Beethoven, wrote music of amazing difficulty. The Sonata for Violin Solo, composed in 1919, runs three-quarters of an hour. After hearing it several times, I'm still certain I don't understand it. Yet there are such interesting things going on that I want to understand it, despite its forbidding facade and high dissonance quotient. The Sonata for Violin and Piano isn't much easier, just shorter. At least Arte Nova makes it easy to investigate for yourself, with first-rate performances and recordings at an amazingly low price. --Leslie Gerber