Edward Polichik's farewell concert with the Montgomery County Masterworks chorus on Saturday night in the National Presbyterian Church was a genuine triumph. After two years with the chorus, Polichik is leaving to spend more of his time in orchestral conducting.

For the young conductor, who two years ago won the Leopold Stokowski Conducting Award and an appearance with the Philadelphia Orchestra, his assignment on Saturday was one of the largest: the C Minor Mass of Mozart. Polichik led the masterpiece with the kind of authority that comes from total securtiy in handling both the well-trained chorus and an orchestra assembled for the occasion.

Over and above these, however, was his knowledge of the score in its latest H.C. Robbins Landon edition, which gives the music a special aura of rightness. Polichik led with fire in the large, dramatic episodes and penetrating insight in the brooding slow pages. The response from both instrumentalists and chorus was notable. The assistance from an unnamed organist was of special merit.

Before the Mass, Polichik took Mozart's familiar motet "Ave Verum Corpus" at the slowest possible tempo but held it together with a kind of mesmerizing control. There were hints of abuse in having the chorus carry over phrases with no pause for breath where both text and music call for a abreath, but the effect was not without its point.

Soloists in the Mozart were headed by soprano Doralene Davis, whose shining soprano was beautiful to hear, particularly as it was a model of style and vocal skill for the others. Jane Vernon was the mezzo, Edward Randell the tenor and Donald Boothman the bass.