The Bach Society Orchestra emerges publicly for its first concert of the season this Saturday evening in what looks like one of the most interesting programs offered around Harvard in a while. The program is a fine example of what instrumental groups around Harvard should strive for: concerts of some non-standard fare for a public overfed with Haydn, Mozart and the Brandenburg Concertos.

If last year is any indication, Bach Soc is one of your best sources of musical inspiration at Harvard this year--a disciplined group with fine soloists and a sense of ensemble. The requisite Bach for the first concert if the Overture No. 3. But even better, there's going to be Beethoven's "Egmont" Overture, Bruch's Violin Concerto in g and Vaughan Williams' "Serenade to Music." Not that most Bach isn't fine and great to listen to; but there are some really sensitive and beautifully written works in the orchestral repertoire which don't come out of Germany or the Baroque period or, more likely, both.

Bruch is known best for his "Scottish Fantasy," which Heifitz has a patent on. But venture over to Sanders Theatre on Saturday at 8:30 to her his Violin Concerto in g, with soloist Stephen Chan; more such evocative and and appealing pieces by less-than-household-names should be presented to Harvard audiences.

That's not all that looks promising for Bach Soc this week; the group is also performing Vaughan William's "Serenade to Music" with the Harvard University Choir. Last year, Bach Soc did RVW's "Lark Ascending," which was beautifully done. The piece for this concert should be well worth hearing, so don't miss it. Bach Soc has demonstrated that it's able to pull off a program combining German baroque and English pastoral or Russian schmalz very well.

Also at Harvard, Peabody-Mason Music Foundation presents pianist Gary Steigerwalt on Friday at 8:30 p.m. in Sanders Theatre. The first American pianist to win the Liszt-Bartok International Piano Competition is Budapest, Steigerwalt will play Haydn's Sonata in F Major, Bartok's Suite Op. 14, Preludes by Debussy and some Liszt and Schumann works, including Schumann's "Symphonic Etudes." Call 266-3314 for more info.

At the same time and around the corner at the Longy school, Music from Marlboro, now in its 13th season, draws nine artists to Cambridge to perform Beethoven's Octet for Winds Op. 103, Gounod's "Petite Symphonie" and a Mozart Serenade. Show up at the door at 7:30 to get a seat. For more info, call 353-3355. The Busch-Reisinger Thursday Noon Recital Series features the Cambridge Symphonic Brass Ensemble this afternoon. Another free event is a concert at the Somerville Public Library, Highland Ave. and Walnut St., this Sunday at 3 p.m. Selections include soprano, flute and harp works--Handel, Britten and everything in between.

Finally, in the Hub: Bach, Rachmaninoff, Scriabin, Chopin and Liszt make up the delegation at the New England Conservatory recital in Jordan Hall, Sunday at 3. It's free, there'll be munchies and the Rachmaninoff. Boston University Wind Ensemble, conducted by Paul Gay, airs Barber's First Symphony and other works at the School for the Arts tomorrow night. The BU Faculty Chamber Music Ensemble begins its season on Monday. Both BU concerts are at 855 Commonwealth Ave. Stay in Cambridge this week for the Bach Soc and other programs which definitely look worthwhile.