In his B minor Mass, Bach made music only a little lower than the angels - music capable of soaring in a plane all its own, sublimely suspended between Earth and sky.

Thanks then to John Marlowe Nielson, who comprehends the essence of good Bach performance: that feeling (dynamics, nuances, phrasing) must be superimposed upon rhythmic regularity and underlying momentum. Hence after several repeat performances of this Mass, Pro Musica has learned to cushion its music from earthly shocks, proceeding clearly, accurately and expressively, with appropriate weight and emphasis.Nielson's custom is to begin simply, without pressure, nor need he fear that his well-prepared singers will fail to build momentum. Indeed, such is the inherent majesty and glory of this music that the conductor's art is sometimes in holding it in check, keeping control of all elements.

The chorus of nearly 40 members was well up to this monumental work. They sang with fine, undistorted tone, and though the first sopranos in the beginning sounded a little light, they soon asserted themselves with enough authority for good balance.

Excellent solos to the contrary, the integral ingredient in this Mass is the chorus. And Pro Musica's good singers, many of them soloists in their own right, mastered a full slate of polyphonic complexities and tonal and technical challenges, singing with often exquisite expression and building to many lustrous and brilliant climaxes. Florid passages were accurately defined, and fugues and other canonic devices came through clean and clear.

Cutting into the Credo with the Easter choruses, the singers beautifully interpreted the drooping emphases of Et incarnatus est and Crucifixus, making them poignant without sentimentality, then soaring triumphantly in the Et resurrexit.

The Sanctus section was both ethereal and brilliant, its triplets pealing out golden layer upon layer, its jubilant fugue, its joyous hosanna. And as the supplicating Dona Nobis pacem (grant us peace) mounted fold upon fold, it seemed exactly the right ending at a time of victory and world hopes for peace.

Bach gave the alto a lion's share of beautiful music in this Mass, and Mary Wescott was a radiant soloist of impeccable style, with a tone both opulent and clearly focused. Her Laudamus te moved with great clarity and accuracy, her Qui sedes was finely phrased. But it was in the suppliant Agnus dei (with Richard Hoyt's beautiful cello support) that she sang with expression that transcended her formidable technique.

JoAnn Ottley was the excellent soprano, here confined to duets only, but these were among the evening's most ingratiating music, notably with Wescott in a flawless Christe eleison and Et in unum Dominum, and with tenor Tom Pike in the Domine Deus. Pike's big, sweet tenor has never sounded smoother or more tonally refined than in the Benedictus qui venit. Completing the roster of soloists was C. Houston Hill, making an auspicious Pro Musica debut with expert baritone solos.