HAVE YOU WONDERED why there seems to be so much Schubert in the air? Jan. 31, 1997 was the 200th anniversary of Franz Schubert's birth. This Friday, at 8:00 pm, the Apple Hill Chamber Players of New Hampshire will be performing a special all-Schubert Valentine's Day concert in the Longy School's Edward Pickman Concert Hall. Their program will feature the famous "Trout" Quintet in A (Op. 114, D. 667) and other pieces. The Longy School itself is presenting a four-month celebration of the master of the lieder which kicked off on Jan. 31 but is continuing through May. All events are free and open to the public. Some of the upcoming highlights:

Sun., Feb. 23 7 p.m. Concert Sonata in A Minor "Arpeggione"; D. 821 Four Impromptus, D. 935, Op. 142; Fantasy in C Major, D. 934

Sun., Mar. 9 7 p.m. Concert: Introduction and Variations on "Trockne Blumen", D. 802; Die Schone Mullern, D. 795

Thurs., Mar. 20 8 p.m. Recital, Shizue Sano, piano: Program to include Fantasy in C Major, D. 760 "Wanderer"

Sun., Mar. 23 7 p.m. Longy Chamber Singers: Program to include Mass in G and the 92nd Psalm: "Song for the Sabbath" (in Hebrew)

Sat., Mar. 29 8 p.m. Guest artists The Brentano String Quartet with violist Samuel Rhodes of the Juilliard String Quartet. Program to include Quartet in G Minor, D. 173