"We have ambitions, but we are secure in our achievements." That was the tone of the Harvard-Radcliffe Orchestra concert last Saturday evening. For his final performance as conductor of the HRO, Michael Senturia chose a difficult program, and directed it smoothly, accurately, and with unusual deliberation.

Senturia conducting Webern and Mozart was prodigy performing prodigies.

The Six Pieces for Orchestra, written, incredibly, in 1909, reflect the expressionism Webern adopted from Schoenberg. They realize his credo, "Once stated, the theme expresses all it has to say; it must be followed by something fresh." At the same time, they embrace the musical principles of the Brahms from which Webern had just emerged (the Six Pieces are only Opus 6). That is, they develop a single, chromatic figure, through varying rhythms and intervals. Every successive point is fresh, but presents only the logical implications of what has preceded.

The original orchestration exults in a luscious palette of tone colors. But in 1928 Webern revised the score for a performance in Berlin. A personal tendency toward leaner writing, as well as the postwar decline in the size of orchestras, led him to reduce the number and variety of the brasses, woodwinds, and percussion.

Performing the 1928 version, Senturia had to achieve both the transparency demanded by the contrapuntal lines in the fifth piece and the massive roar called for by the ending to the fourth. He achieved both. He brought forth each instrumental entrance with discerning care, and he chose tempos that made each piece cohere individually, and with the other five.

The other triumph of the evening was Mozart's "Jupiter" Symphony, No. 41. The HRO displayed its impressively solid strings and wood-wind ensemble. Senturia followed a sharp initial attack with a fine, deliberate tempo. He concluded the fun of the third movement (Allegretto) with a stately allargando. And in the fugal stacking of themes at the final coda, he delineated each important voice.

Less gymnastic than their title would suggest, Erik Satie's Trois Gymnopedies (1888) are pastoral melodies with an extremely simple accompaniment of strings and harp. But even in his most restrained mood, Satie could not resist a final playful tweak: the three pieces end on the "wrong" chord (subdominant); but nobody notices this joke any more, and the Trois Gymnopedies pass, to Satie's undoubted horror, as incorrigibly romantic.

The program claims that the HRO was assisted by the Cambridge Ballet Theater. That is untrue. The opening "Air" and two "Gavottes" from Bach's Third Suite in D. Major had the misfortune to introduce dancers encumbered with awkward and ludicrous choreography. A troupe of rheumatic frogs would have been more graceful, although it must be added that soloist Richard Hendrik improved when the tempo picked up in the Gavottes, where Senturia got the orchestra to produce bouncy dynamic contrasts.

If Senturia and the orchestra had to struggle for their success, at least they struggled in rehearsal, not in the performance itself. The audience rewarded their achievement with a standing ovation, and the orchestra passed the honor on to its conductor with a plaque. The performance, both during the last three years and Saturday night, justified this twin accolade.