The fall classical season really gathers steam this weekend on many fronts, with traditional ensembles, guest artists from as far away as Germany and a new venue for a popular pops orchestra.

The Palo Alto Chamber Orchestra welcomes cellist Michelle Djokic to help open its 45th season. The program embraces a string quartet by a young (11 years old) Mendelssohn, Jean-Baptiste Lully’s Baroque Piece de Concert and Suites for Cello and Strings by Lou Harrison. Saturday, 8pm; Eagle Theater, Los Altos High School; $5–$15. The San José Chamber Orchestra, under the direction of Barbara Day Turner, presents “There Is a Time.” Vivaldi’s Flute Concert (Il Gardelino) will be performed by guest artist Viviana Guzman. The evening also features The Seasons by Howard Hersh, who studied composition at Stanford, and Norman Dello Joio’s Meditations on Ecclesiastes. Sunday, 7pm; Le Petit Trianon, San Jose.

All the way from Germany comes the Fauré Piano Quartet courtesy the San Jose Chamber Music Society. The violin, cello and piano ensemble will perform works by Mahler, Brahms and Schumann. Friday, 8pm; Le Petit Trianon, San Jose; $30–$42. Henry Mollicone’s Winchester Orchestra gets its new season started with 13-year-old guest violinist Stephen Waarts taking on the challenge of Paganini’s Concerto no. 1 for Violin and Orchestra. The program also includes Schubert’s Overture in the Italian Style and selections from Carmen. Saturday, 7:30pm, West Valley College Theater, Saratoga; and Sunday, 7pm, Trinity Cathedral, San Jose; $10–$20.

Master Sinfonia Chamber Orchestra, the in-house symphony of Foothill College, performs Handel’s Water Music and Haydn’s Symphony no. 103. Saturday, 8pm, Valley Presbyterian Church, Portola Valley; and Sunday, 3pm; Los Altos Methodist Church; $5–$20. El Camino Youth Symphony starts its 48th season with a program of Dvorak, Prokofiev and Liszt. Saturday, 7:30pm, Flint Center, Cupertino; $6/$12. Baroque leads the way for the 30-member vocal group the California Bach Society, with a performance of Purcell’s Hail! Bright Cecilia (1692) and Handel’s Acis and Galatea (1718), a single-act dramatic work in a pastoral vein. Saturday, 8pm; St. Patrick’s Seminary, Menlo Park; $30. Also in a vocal groove, the SJSU Concert Choir and Chamber Singers offer “There Will Be Singing,” a night devoted to Schumann, Schubert and Brahms. Friday, 7:30pm, Campbell United Methodist; and Saturday, 7:30pm, First Congregational Church of Palo Alto; $10–$25.

This weekend also marks the beginning of a new six-concert season and a new venue for the California Pops Orchestra. The 65-member group, led by Kim Venaas, had to scramble for a new performance space recently and was able to settle at Calvary Church in Los Gatos. The opener shows off the Pops at its best, doing favorite tunes form Broadway and movie soundtracks. Sunday, 3pm; $10–$35.

Speaking of pops, one of the most names in the business pops up as Frank Sinatra Jr does a benefit show with Symphony Silicon Valley. The concert, preceded by a champagne reception, raises money for the Stroke Awareness Foundation. Saturday, 8pm; California Theatre, San Jose; call 408.879.8433 for ticket info.