Ozawa Hall at Tanglewood in the Berkshires was the scene last week of an incredible chamber concert, performed by Ebene String Quartet. These four young French musicians have been described as “a string quartet that can easily morph into a jazz band.” That’s exactly what they did, with Mozart and Tchaikovsky on the first half of the program, and jazz improvization on the second half. Their music is captivating and electric. They give new energy to classical music and were equally at home doing jazz. The improvizations in this concert were taken from “Fiction,” their new award-winning jazz and world music album. This new generation of musicians is converting listeners of jazz into avid fans of the chamber music genre — and vice versa.