When the National Symphony Orchestra is good, it is very, very good. And so it was last night when it opened the first of its "Six-Pack of Beethoven" with playing the quality of which belied the quaint vulgarity of the series title.

Erich Leinsdorf led the orchestra with his customary clarity and control. If his approach to Beethoven is not the type to inspire love, it does command respect. The "Eroica," Symphony No. 3, opened with the mounting insistence of its chain of chords making the most of each crescendo. The horns were thrilling as the return to the tonic E-Flat was sounded against the vestigial dominant, and if the vastness of the recapitulation was lost in speed, the interpretation convinced. The second movement suffered the most from the rushed tempo, and the decrescendo from the grief of the famous funeral march was too protracted for the peaceful coda to achieve its full potential. There was strength behind the joy of the scherzo, however. And the staggering finale found Leinsdorf in a rare expansive mood: The oboe and violin were allowed to linger on their shared theme, and the swift change to poco andante ushered in a powerful finale.

At the center of the program was Beethoven's Concerto No. 4 with pianist Emanuel Ax. From the opening five-bar solo, his was a passionate reading of a delicate work, often at odds with the conductor's approach. However, the musical dialogue was a fruitful one, especially in the andante's distinctive dialectic of staccato strings and tender piano phrases. A Luftpause might have been welcome, but it would be difficult to forget the austere sensuality of the whispering violins as their climax was interrupted by the final rondo.

The concert opened with the "Lenore" Overture No. 3, with some wild winds and impressive offstage trumpet work.