Barenboim on YouTube. How do musicians arrive at their views of what the particular character of a piece should be? Pianist and conductor Daniel Barenboim talks about this eternal dialogue between performer and piece in a series of five-minute videos available on his YouTube channel. He has touched on Mozart, Brahms, and Chopin so far, and you might listen differently to one famous piece after his segment on Beethoven. Barenboim notes that the opening movement of the "Moonlight" Sonata is not about moonlight, but is really a funeral march. His is not the first debunking of a nickname not of Beethoven's choosing, of course, but when the person explaining can turn to the keyboard to make the point with an excerpt from Don Giovanni, the point is made powerfully - and beautifully. - Peter Dobrin

No matter how beautiful the piece . . . it's going to be neglected if written for an unconventional ensemble. So the Philadelphia Chamber Music Society's concert at 3 p.m. Sunday at the Perelman Theater augments the Johannes Quartet with notable string soloists - violist Kim Kashkashian and cellist Marcy Rosen - for Brahms' String Sextet Op. 18. The more tuneful of the composer's sextets, Op. 18, has youthful, surging melodies and pockets of melancholy and self-doubt, and it's without the occasional misjudgments one hears in early Brahms. His first symphony wouldn't be finished for 16 years, but the 1860 sextet often feels like a practice symphony, though one that's fully realized on its own terms. The program also includes the Bartók String Quartet No. 3 and Mozart's Quartet in B-flat, K. 589. Information: 215-569-8080 or www.pcmsconcerts.org. - David Patrick Stearns