. It's not the melodic material that makes the piece so special, for the theme is little more than a few short phrases based on folk sources (that the orchestra helpfully played during Alsop's short talk), but Bartok put those fragments through so many permutations that it was as if he were tying and untying different knots into the same string all night long. Following Bartok's instructions, Alsop had divided her string section in two and then pitted one half against the other, especially in the furious call-and-response passages in the dance sections. The push-and-pull of the rhythms was given some muscle by the emphatic piano, tympani, and celesta (a small piano that replaces the strings with metal plates) arranged behind the strings. But this horn-less version of the orchestra was also capable of great delicacy, most notably when the chiming celesta and harp added to the eerie nocturnal feeling of the pizzicato strings in the third movement. When this recording is finally released, it should give a real boost to the BSO's reputation, for the strings played with all the rich color and precision one could hope for. One wishes that Alsop would program more such challenging and satisfying fare, but she still faces resistance from her audience. That was clear in the men's restroom during the intermission immediately following the Bartok. While waiting in line, an elderly gentleman in a mustard-yellow blazer declared to one and all in a tone of assumed knowingness, "I wonder what Bach and Mozart would have thought of that? They would have said, ‘How did it all go so wrong?'" This man was presumably happier when, after intermission, the orchestra returned to play Beethoven's "Emperor" Piano Concerto No. 5 with soloist Andre Watts. After all, this was sumptuous music, full of the grand gestures of the 19th-century vocabulary. Even at age 63, Watts is an exceptional pianist, banging out the loud passages with such crisp authority that when he pulls back for the quieter sections, he sounds incredibly tender but can still be heard clearly throughout the hall without amplification. Watts, a 1972 graduate of the Peabody Conservatory, betrayed no strain at all on the quick triplets and long strings of eighth and 16th notes. This music sounds so familiar now that it's easy for our friend in the men's room to forget how iconoclastic Beethoven sounded in 1800 when he premiered his first symphonies. One would assume that Bach and Mozart, both revolutionaries in their own time, would have embraced Beethoven's breakthroughs, just as they would have embraced Bartok and John Adams.