The first-class clarinet festival currently at Catholic University continued last night with an elegant concert at Hartke Theater by Karl Leister and the Festival String Quartet.

Leister, a well-known name among clarinetists, is the principal clarinetist of the Berlin Philharmonic and one of today's great exponents of the instrument. His style is marked by an unfailing musicianship which turns the clarinet into a vehicle of liquid beauty. Producing a pure, seamless stream of sound from top to bottom, he maintains a silken tone through the most demanding passages. With a seemingly absolute control over dynamics, he can spin phrases of exquisite shape, creating supple melodic curves that were a particular delight yesterday in Weber's Clarinet Quintet.

The consistently veiled, somewhat introverted quality of Leister's style, which proved especially effective in the shifting moods of Reger's Clarinet Quintet, contrasts strongly with the characteristically bright American approach. Though more brilliance might have heightened the drama of Weber's music, Leister found a wide expressive range without it. The Festival String Quartet contributed consistently sensitive playing to the evening.

In addition to varied activities beginning at 9 o'clock each day, Stanley Drucker performs at Hartke Theater tonight at 8:30, followed tomorrow evening at 8:30 by the American Camerata and a trio of clarinetists at the Library of Congress.