The Beaux Arts Trio, the world's preeminent piano trio, is celebrating its 50th anniversary. It's maintained a very high standard through several personnel changes because of the one constant, pianist Menahem Pressler, an impeccable artist who still sounds great. These days he's joined by cellist Antonio Meneses (since 1998) and violinist Daniel Hope (since 2002), and their recent CD of Dvorak's Dumky Trio and Mendelssohn's D Minor Trio is excellent, even though it doesn't top the recording made during the Pressler, Cohen, and Greenhouse era--the Mendelssohn is gutsy, lush, and tender in all the right places, and the Dvorak is passionate, though at times the strings are a little scratchy. At Ravinia the group will play Beethoven works for piano trio over two evenings. The Monday program begins with the first two opus 1 trios, in which Beethoven broke with convention by enlarging the scale--both have four movements instead of three--and distributing the writing more evenly among the parts. They're great works, combining lyricism, impetuosity, and inventive thematic development. Yet the two opus 70 trios on the program are in another league: composed after his Sixth Symphony, they show Beethoven at the height of his powers. The Trio in D Major, the highlight of this program, is a masterpiece in three movements. The first is exhilarating, dignified, and grand, as is the more jovial third. But the emotionally powerful adagio, which gives this work its nickname, the Ghost, is one of Beethoven's most extraordinary movements. Its haunting opening theme, with its wheezing strings and stately response from the piano, can be heart wrenching, yet with the change of a note or chord it becomes uplifting, transforming despair into optimism. The Tuesday program will include the third opus 1 trio, along with the Archduke and the Variations on "Ich bin der Schneider Kakadu." Mon 7/4, 7 PM, Martin Theatre, Ravinia Festival, Green Bay and Lake Cook Rds., Highland Park, 847-266-5100, $10-$40.