R. M. Campbell, P-I

Opus 7 has been celebrating its 10th year of business all season, which concluded this weekend with a pair of concerts.

And rightly so. Along with a handful of other vocal ensembles, Opus 7 is one of the reasons some might say Seattle is in a golden age of choral singing. Not only does good singing abound, the music heard is incredibly diverse, covering century upon century of vocal tradition from the distant Byzantines to 21st century America.

While these groups have been assembled with limited funds, other resources such as musical sophistication, inquiring minds and ambition are found in plentiful supply.

Loren W. Ponten founded Opus 7 a decade ago with six of his friends. A bass-baritone, the conductor was the seventh. Thus the name. Since then, Ponten stopped singing and the number of singers grew to a core group of about 20. This weekend there were nearly 30, except in the final work in which former members of the group, about 10, joined the ensemble.

Inevitably such choral groups, which are underpaid, if at all, and overworked, suffer from turnover. In Opus 7, half of the original six singers, beside Ponten, have remained. Almost half of the group joined in the past three years. However, there was no hint of the newly arrived in Opus 7’s musical poise Saturday night at Bastyr University Chapel, at the north end of Lake Washington.

I don’t think I have ever heard the ensemble sing with such razor precision or perfectly ordered balance. Phrases were cleanly cut and perfectly molded. Resonance is not so much sought after but purity. Everything on Saturday was crystal clear. As the singers in Opus 7 have grown, so has their music director.

Over the decade, repertory changed in various ways. Even though it remains eclectic, the group’s focus is 19th and 20th century a cappella music, particularly the new.

On Saturday night, the music ranged from C. Hubert H. Parry (1848-1918) to composers who worked in the early to the middle part of the last century (Finzi, Barber, Ravel, Ives) to living composers such as Bern Herbolsheimer, John Muehleisen, Gwyneth Walker and David Griffiths. There were premieres of two works commissioned by Opus 7: Walker’s “God’s Grandeur” and Griffiths’ “Te Deum.”

It may seem obvious but not everything was of equal interest. Griffiths’ “Te Deum” was too long and seemed to wander on a bit. However, it provided plenty of challenges to the singers, which they met heroically. Walker’s new work appeared rather parched in places. However, Ives’ “67th Psalm” had much to offer, as did Paul Sjolund’s “Love Lost” cycle, Ravel’s “Nicolette” and Alice Parker’s arrangement of “Hark I Hear the Harp’s Eternal.”

As attractive as these kinds of program are on paper, it is important sometimes to anchor them with music that is widely acknowledged to be of the first order.

It was no accident that every Silk Road Project concert last week had a point of reference to the standard repertory. Novelty can satisfy one’s curiosity but not necessarily all other departments.