Between current artistic partner Christian Zacharias (completing the first year of his tenure) and partner-in-waiting Thomas Zehetmair (whose April preview engagement was prolonged by volcanic ash), the St. Paul Chamber Orchestra's audiences have not lacked for Z's this season. But there is no confusing these end-of-alphabet Germans -- pianist and violinist, respectively -- who now account for half the names on the orchestra's roster of partners.

Friday morning's Zacharias-led, slightly tired-sounding season finale, which offered music by Robert Schumann, Bernd Alois Zimmermann and C.P.E. Bach, was prefaced by a gracious conversation with longtime keyboard player Skip James, who embarks on an active retirement following these concerts. His ovations have been earned.

The second surviving son of Johann Sebastian, Carl Philipp Emanuel Bach (1714-1788) is a great composer cheated by history. Caught up in the profound shift from late baroque to Viennese classicism, he has more to teach us about stylistic change than almost any other musician. Mercurial and fragmented, with undercurrents of anxiety, his pieces are given to neck-snapping emotional juxtapositions and an almost postmodern mix of styles.

One caught glimmers of this in Zacharias' performances of an E-flat Sinfonia and a D-minor Keyboard Concerto, in which he doubled as soloist. Often, however, the music seemed de-energized, its contrasts muted. And deploying a 9-foot Steinway in a 1748 concerto is rather like dispatching an 18-wheeler to do a hand truck's job.

Written in the dead of winter, Schumann's "Spring" Symphony (a.k.a. No. 1) is hardly the composer's most sophisticated score, but its lyric radiance is hard to resist. Friday morning's reading had its share of felicities -- balances were irreproachable -- yet felt sluggish; especially in the opening movement, it wanted the sense of elation and the singing line that make Schumann the quintessential romantic.

Like Schumann, Bernd Alois Zimmermann (another Z!) attempted suicide; unlike Schumann, he succeeded. Born at the end of the first World War, he was drafted into the German army during the second, and seems never to have recovered. (His pacifist opera "The Soldiers" has won a toehold in the global repertory.)

Zimmermann's "Rhine Carnival Dances," for 13 winds, finds him in an atypically upbeat mood. Bumptious and sly, delectably played, it was, all six minutes of it, the best thing on the program.

Larry Fuchsberg writes regularly about music.