The Zagreb Philharmonic Orchestra sounded a note of pensive poetry in its debut at the Kennedy Center last night. Currently making its first extensive American tour, the ensemble under music director Pavle Despalj plays with a veiled, self-contained quality that contrasts strongly with the extroverted brilliance characteristic of many orchestras in this country.

Apart from persistent horn problems, the musicians showed solid strengths, particularly in the string section, reaching within to produce a sound of soulful depth yet never lapsing into trite or unrestrained emotional displays. Under Despalj's carefully modulated pacing, they revealed the full measure of their expressive style in the second half of the program, which was devoted to Tchaikovsky's Fifth Symphony. Despalj's ability to sustain a broad pulse produced some powerful passages, including a hypnotic, slow-motion unfolding of the contrasting theme in the first movement.

Valter Despalj joined the ensemble as soloist in Dvorak's B-minor Cello Concerto and turned this into a highly personal statement, rich in subtle insights and intimate exchanges with the orchestra. The program opened with a "Chorale for Strings" by the contemporary Yugoslavian Stanko Horvat. Heavily influenced by the Polish composer Penderecki, the work set massed string sounds against the archaic strains of a Gregorian chant on a few solo instruments.