Bach's mighty Mass in B minor may be the ultimate challenge for a small choir and orchestra largely driven by love for the music and its composer. And when those forces bravely pull it off, as did the Denver Bach Society over the weekend, this extraordinary masterpiece becomes a testament to the power of passionate commitment.

Led by Michael Shasberger, the seven-year-old organization presented the B-minor Mass twice over the weekend at Christ Episcopal Church, undaunted by the sheer magnitude of the music. This amazing work is endlessly rich in full-blooded harmony and complex counterpoint that tests the will and stamina of even the most accomplished chorus. Add to those challenges a large number of exposed instrumental and vocal solos, and the journey through the Mass can prove a fatal one if the spirit and the technique are not up to snuff.

A few blemishes aside, Saturday's reading proved a stirring experience, lifted by the performers' talents and their obvious joy in performing this music for the ages.

The Bach Society Chorus consisted of the Canto Deo Chamber Choir (prepared by Jonathan Brown) and the Boulder Bach Festival Chorus (led by David Harris). Tucked into a corner of the spacious church, the combined choir was ably accompanied by the Mercury Chamber Ensemble.

From the opening Kyrie, it was apparent that Shasberger had no interest in weighing the Mass down with sluggish, introspective intensity. Instead, tempos were fluid but never rushed. Clarity of counterpoint was uppermost in his mind as he set out to create a lightness and transparency of texture. The result was a comfortable balance of instrumental and choral forces that permitted the listener to bask in the magnificence of Bach's incomparable skills - albeit sometimes at the expense of profundity.

If the first Kyrie lacked the desired depth of devotion and supplication, the conductor was able to draw out all of the unbridled ecstasy of the Gloria that soon followed. The monstrously difficult choral fugues were met mostly with secure ensemble, though a few frayed ends appeared as the lengthy work unfolded. The dramatic contrast of the paired Crucifixus and Et resurrexit made a strong impression, though, wonderfully matched by the stirring work from the Mercury players.

Contributing in fine fashion to Saturday's performance were the vocal soloists: soprano Maureen Sorensson, mezzo Marjorie Bunday, tenor Todd Teske and bass Bobb Robinson. The women fared a bit better than their male colleagues, but all of the solos and duets proved effective and often deeply moving (notably Bunday's expressive handling of the Agnus Dei and the heartfelt Christe, sung in duet with Sorensson).

The Mercury Ensemble provided consistently expert playing, highlighted by solid individual moments from the trumpet trio led by Daniel Leavitt, flutist Alaunde Copley-Woods, oboist Elizabeth Hardin and concertmaster Lynne Glaeske.

Denver Bach Society

• Grade: B

• When and where: Saturday at Christ Episcopal Church

Marc Shulgold is music and dance writer. 303-954-5296 or shulgoldm@RockyMountainNews.com