Self-styled "professional" chamber choruses are a dime a dozen. Every little vocal group that can make a couple of bucks today calls itself professional whether its singers have any business in that league or not. So it is a pleasure to hear a chamber chorus like Paul Hill's Washington Singers that deserves the label. Hill has collected 18 fine voices for his ensemble, and the Bach program they presented at the National Presbyterian Church on Saturday attested to their professional quality.

The soloists for Cantata No. 106, "Gottes Zeit ist die allerbeste Zeit," and the "Magnificat," drawn from the chorus, were excellent. David Crawford, who has a marvelously resonant sound, could have projected a more rhapsodic "Heute wirst du mit mir" in the cantata and a more robust "Quia fecit mihi magnam" in the "Magnificat," and tenor Robert Cornett was outweighed by the orchestra in his cantata aria, but they handled their other assignments well, and sopranos Carol Bernard and Lea Joergensen and altos Maurine Zamberlan and Sarah Bloxham sang beautifully.

The chorus itself, even when split into two nine-voice semi-choirs for the motet "Der Geist hilft unser Schwachheit auf," had the kind of full-bodied, focused sound that is the hallmark of well-trained singers.

Hill's conducting of this music, however, appeared curiously detached; he seemed to pay little attention to what the orchestra was doing. As a result, some marvelous possibilities for interaction between instruments and voices were overlooked, and there were some difficult moments when signals got crossed altogether. Diction was not particularly expressive and tempos did not always work. But these were problems that plagued the first half of the program in particular. The concluding "Magnificat" was full of fine music making.