Why four players are suited to trio sonata

What: Victoria Baroque Players: The Art and Craft of the Trio Sonata When/where: Saturday, 7:30 p.m., Church of St. John the Divine (1611 Quadra St.) Tickets: $28, seniors $25, students and children $5. In person at Munro’s Books, Ivy’s Bookshop, and Long & McQuade What: Brass Extravaganza When/where: Sunday, 2 p.m., St. Andrew’s Cathedral (740 View St.) Tickets: Admission by donation

On Saturday, the Victoria Baroque Players will launch its seventh season with a chamber-music concert featuring four of its core members: flutist Soile Stratkauskas, its founder and artistic director; violinist Christi Meyers; bassoonist Katrina Russell; and, on harpsichord and chamber organ, Michael Jarvis.

The appealing program is devoted almost entirely to trio sonatas by Bach and Handel, original works as well as arrangements.

So this seems like a good time to answer a question I hear often, one you might be asking after reading the preceding paragraphs: Why does it take four people to play a trio sonata?

This term applies to Baroque sonatas for two melodic instruments plus basso continuo; they are trios because they have three lines of music.

But there are two components to basso continuo: a bassline, plus an improvised accompaniment that supplies a harmonic backdrop for the music, the latter requiring, of course, an instrument capable of playing chords. (A continuo player’s part comprises a bassline beneath which are numbers that encode the required harmonies.) In practice, basso continuo usually features two players, one to sustain the bassline, the other to supply the harmonies.

On Saturday, the bassoonist will play the bassline while the keyboard player doubles the bassline with his left hand and improvises an accompaniment with his right.

And so, yes, a trio sonata can be a quartet. A trio sonata can be a solo, too, if performed by, say, a single keyboard player.

Around the late 1720s, Bach composed six novel trio sonatas for the organ, giving one musical line to each hand and one to the feet. (He apparently wrote these for his organ-playing eldest son, Wilhelm Friedemann, in some cases drawing on earlier works.) So pure is the part-writing in these pieces that they lend themselves readily to being arranged for chamber ensemble, and such arrangements accord with the very flexible attitude toward instrumentation that prevailed in the Baroque era.

Saturday’s program will include three of the organ sonatas, two of them arranged for the complete foursome, the other rendered, like some of Bach’s own flute sonatas, as a duo for flute with obbligato harpsichord rather than basso continuo — that is, with Jarvis playing the lower two parts, one with each hand.

(Wait, so a trio sonata can also be a duo? I know, I know …)

The program also includes a little one-movement Bach trio plus a pair of his Two-part Inventions, arranged for violin and bassoon.

All of these arrangements are especially welcome given that Bach’s output of original chamber music was comparatively small.

Among all this Bach will be selections from Handel’s Op. 5, a collection of modest but delicious works published in 1739 as Seven Sonatas or Trios. (Handel, too, drew much of the music from earlier works.)

The program ends, in fact, with Handel, with the stately Passacaille (a set of ground-bass variations) from the fourth sonata, or trio, but really a quartet, or. . . This year marks the 125th anniversary of St. Andrew’s, the red-brick Catholic cathedral at the corner of View and Blanshard, which is, among other things, a splendid venue for music.

In January, the cathedral began hosting a series of concerts honouring the anniversary, to date including appearances by the Victoria Cello Quartet, the Arion Male Voice Choir and the Emily Carr String Quartet. On Sunday, the series will continue with music for brass instruments, which make a splendid noise in the cathedral’s grand, resonant nave.

The concert features the Victoria Brass Quintet, which includes three members of the Victoria Symphony, and another local quintet, Brasstastic. They will perform separately, together, and antiphonally, making some use of the cathedral’s balcony, and will sometimes be joined by the cathedral’s organist, Kathleen Edge, who will also play a few solos.

Much of the program spans the late 16th through early 18th centuries — Gabrieli, Charpentier, Campra, Handel, Pachelbel — though it also includes music by the contemporary American composers Morten Lauridsen and Anthony DiLorenzo as well as Cavatina Pacifica, a work by local trombonist Ian McDougall that evokes peaceful waters around Vancouver Island on a still day.