The St. Paul Chamber Orchestra is losing something valuable this month: pianist and conductor Christian Zacharias, who is giving up his position as one of the orchestra's artistic partners, a post he has held since the 2009-10 season.

Not all of these partnerships have been happy, productive unions, though none, it appears, has been a disaster, either. The idea, initiated some years ago, was to replace the music director position with five or six musicians — star soloists, usually — who would play with the orchestra several weeks a season over a period of three years or more.

The format is a variation on former orchestra president Deborah Borda's three-conductor scheme introduced here in the late 1980s. Given its focus on frequent changes in personnel, the format might be thought appropriate for audiences with short attention spans. The result, at its best, however, has been increased variety in both programming and performance styles. The downside is a shortage of conductors, which means the orchestra often performs nowadays without a conductor. Good as this ensemble is, the result has sometimes lacked the attention that a conductor can provide.

The German-born Zacharias, who turned 66 last Wednesday, is that rare bird: an important pianist who is also an accomplished conductor. He has led the orchestra in provocative, unconventional programs. The first of the three programs he is presiding over here in successive weeks as a farewell to the orchestra include works by Beethoven, Carl Philipp Emanuel Bach (the second and most gifted of J.S. Bach's sons) and the contemporary French composer Thierry Escaich.

Even the layout of these works Friday night at the Ordway Concert Hall in St. Paul was interesting. Zacharias put two of Bach's brief symphonies — works from his so-called "Berlin" period in the 1750s — at opposite ends of the first half, with Escaich's "Baroque Song for Orchestra," a piece from 2007, played between them.

The symphonies are post-Baroque, but they have enough of the earlier style to fit nicely alongside Escaich's "Baroque Song," which expands — and expounds — on imaginary chorales from the Baroque era, as if it were improvising on this music while moving it forward two centuries. "Baroque Song" is cleverly written. The whirling arabesques in the woodwinds that begin the first of the work's three brief movements sound like the lead-in to a public radio news hour, and yet the piece goes beyond parody. It creates its own sound world.

Zacharias drew pungent performances of all three works from the orchestra. For the second half, he took on double-duty, playing and conducting Beethoven's Piano Concerto No. 4. This was a strong performance, intimate in its contours and feeling and surprisingly flexible in tempo — more elastic than one usually hears in the Beethoven concertos these days. The playing was fluid but precise. Zacharias chose the longer of the two first-movement cadenzas, giving it an energized, improvisatory flair.

Michael Anthony is a Twin Cities classical music critic.