No matter how arcane Piffaro the Renaissance band becomes in its programs, the result is blessedly consistent: a lot of thoroughly winning music that you've never heard and may never hear again.

However true to form the group was at its season-opening concert, "Iberia Old and New," the performance standard on Friday at St. Mark's Church was probably closer to an average day at a 16th-century Madrid cathedral than we would like: Two regular members were absent, and though their fill-ins were mostly just fine, the group sometimes lacked its effortless cohesion in this all-instrumental program.

The music always rang through in a program devoted to seldom-heard sacred and secular works from mid-1500s Spain - not the composers who normally define the Spanish Renaissance (Victoria and Morales), but the court and cathedral-imported composers from Northern Europe, much of whose work was lost in the 1755 Lisbon earthquake.

So you had to relish the few surviving bits of then-famous Philippe Rogier and George de La Hèle, as well as the better-known Pierre de Manchicourt.

Piffaro has a way of playing instrumental versions of vocal polyphony with artfully arranged layers of sound that clearly delineated the working parts of the music - particularly in double choir passages of La Hèle's Missa "Praeter rerum seriem" - more than in some of the best voice-only renditions.

Without words and the subtle vocal responses to them, the experience is more cerebral, but with a welcome side effect: Elements you take for granted in this highly formalized music can emerge with new meaning, such as the majestic uncertainty that ends many pieces. The music seems to reach some sense of ultimate truth in the penultimate phrase, only to conclude by contemplating the incomprehensible infinite.

In secular works, Piffaro embraced the 16th century's lack of standardized ensemble with arrangements featuring trios of bagpipes or forerunners to the modern bassoon - conceptually not unlike the current generation of New York downtown composers who write for crazy lineups like 200 electric guitars. Unlike them, Piffaro's music-making has a transparency that reveals the music's shifting confluence of ethnicities from Arab to Flemish to Jewish - even if bugs hadn't entirely been worked out in some of these adventures.

David Patrick Stearns at dstearns@phillynews.com.