The University Choir is an outstanding choral group. Their performance of the Bach Cantata No. 80, Ein feste Burg ist unser Gott, should be well worth hearing. The Fisk organ in Appleton Chapel is particularly suited to this sort of program.

The Brandeis Chamber Orchestra is playing concerti with three soloists all familiar to Cambridge audiences: violinist Robert Koff, harpsichordist John Gibbons, and one of Harvard's most popular professors--Luise Vosgerchian. A program featuring all original instruments.

ELIOT HOUSE LIBRARY. Sarah Brink, harpsichordist, in recital. Works of L. Couperin, Frescobaldi, Boismortier, and Bach. Free. Friday, October 26, 8:30 p.m. KIRKLAND HOUSE JCR. Hanni Schmid-Wyss, pianist, in recital. Works of Beethoven, Rossini, Bartok, and Mendelssohn. Free. Friday, October 26, 8:30 p.m.

LONGY SCHOOL OF MUSIC. Scott-Martin Kosofsky, recorder player, in recital. Works of van Eyck, Hotteterre, and Telemann. Tickets: $2.50. Friday, October 26, 8:30 p.m.

SANDERS THEATER. Harvard University Band, in concert, with the world's largest tuba. Tickets: $1.50 (students: $.50). Friday, October 26, 8:30 p.m.

DUNSTER HOUSE LIBRARY. David Lawrence, tenor; and Liz Hershey, lute. Sixteenth-century songs. Free. Saturday, October 27, 5:30 p.m.

MEMORIAL CHURCH. Harvard University Choir. Choral Evening Service with Bach's Cantata No. 80. Free. Sunday, October 28, 4:00 p.m.

SANDERS THEATER. Brandeis Chamber Orchestra. Works of Mozart, C.P.E. Bach. Tickets: 253-7764 (day), and 864-5530 (night). Monday October 29, 8:30 p.m.