Seventeen years into their founding, appearance by the Tetzlaff Quartet remain extremely rare. One glance at the schedule of the quartet's founder, renowned violinist Christian Tetzlaff, and the reason becomes clear. In the months preceding the quartet's seven-city U.S. tour in April, Christian Tetzlaff will perform orchestral, small chamber, and solo concerts in Berlin, Salzburg, Miami, Strasbourg, St. Petersburg, Lübeck, Zürich, Boston, New York's Carnegie Hall (one of three Carnegie appearances this year), London, Paris, and several other European cities.