Imagine a composition with the theme "God is punishing you, and you deserve it." Imagine further that it is a masterpiece, wonderfully varied in the music of its seven segments, fascinating to music lovers of many kinds and deeply consoling to those who believe that, in fact, God is punishing them and they do deserve it. Finally, imagine such a work drawing enthusiastic applause from a downtown audience of Washington office workers whiling away their lunch hour.

Only one composer could do that--Johann Sebastian Bach--and he did it yesterday, with the considerable assistance of conductor J. Reilly Lewis and the Washington Bach Consort. It was the second concert in the consort's 11th season of free noontime cantatas, given on the first Tuesday of each month from October to June at the Church of the Epiphany, 1317 G St. NW.

The same group performs a free "basically baroque" Rush Hour Concert Series at St. John's Church on Lafayette Square NW at 5:30 p.m. on the last Tuesday of each month--essentially a service for those who are waiting for the HOV restrictions to be lifted on Route 66 and would rather not do it at a "happy hour." These concerts are among the redeeming factors that make the Washington area, in spite of everything, a civilized place to live.

The message of Bach's seldom-heard Cantata 114, "Ach lieben Christen, seid getrost" ("Ah, dear Christians, be consoled"), was stated most clearly in its third movement, a recitative sung with the proper simple elegance by bass Thierry van Bastelaer: "O sinners, bear with patience what you have brought upon yourselves by your misdeeds."

Its emotional overtones were searchingly explored in a tenor aria (sung with light tone, clear diction and restrained ornaments by Stephen White) that avoids despair by appealing to God's mercy. The tenor voice was intertwined with a limpid flute solo, played expertly by Karen Johnson, that illustrated and reinforced its changing moods.

Soprano Gisele Becker gave depth to a simple chorale melody sung with minimalist organ and cello accompaniment, and countertenor Roger Isaacs brought the right freshness and optimism to his elaborate aria on conquering the fear of death. All of these fine soloists are members of the consort's chorus, which is--and sounds like--a dozen singers of solo quality.