No doubt the greatest music to the largest number of ears at last night's National Symphony birthday concert for Armand Hammer, 84, came in the form of the monetary gifts he dispensed at the end--to the orchestra and to Carnegie Hall.

Along the way, though, there was some beautiful playing, especially Isaac Stern's eloquent, almost soulful performance of Max Bruch's First Violin Concerto. One says "almost" mainly because this is not a work which one has come expect a soloist to play with such depth of expression. Another perfectly respectable rendering on the same stage Saturday night by the young Shlomo Mintz was closer to the prevailing norm.

But instead of playing the slow movment, for instance, as a conventional virtuoso lyric piece, Stern transformed it into something closer to an aria, or a meditation. He can play softer and with a more uniform quality of tone than most violinists and he uses these traits to sound more like a singer--extending phrases almost to the breaking point without ever losing the line.

Some use this concerto mainly to display their technique, but with an interpreter as fine as Stern, who cares about just technique? He had a few uncertain technical moments, particularly at the beginning--hardly surprising for an man in his early sixties who was released from an Israeli hospital only about a week ago after gall bladder surgery. The accompaniment under Rostropovich was spirited, though if he were going to repeat it he should tone down the orchestra in the first movement; Stern was sometimes blanketed.

The other outstanding music of the evening came in excerpts from Prokofiev's ballet, "Romeo and Juliet," which Rostropovich and the orchestra are now preparing to record for DG. The early excerpts were promising, but by the time of the "Balcony Scene," the lower strings were playing the first love theme with quite remarkable richness of tone. Likewise, the concluding "Death of Tybalt" was rhythmically electric.

The opening was a pleasant romp of a performance of Barber's Overture to "The School for Scandal," which along with Bizet's Symphony in C must be the finest work ever written as a conservatory graduation piece.

Baritone Robert Merrill sang three arias: "Di Provenza il mar" from "Traviata," which he still sings almost as well as he did 40 years ago; "Largo al factotum" from "The Barber of Seville," which he sings less well than then; and "I Got Plenty o' Nuttin' " from "Porgy and Bess," an aria whose literary message seemed quite beside the point after Hammer came on the stage to bestow his benefactions.

No doubt as a gesture toward Hammer's long history of association with the Russians, Rostropovich ended the evening with Tchaikovsky's 1812 Overture, complete with brass choirs in the balconies, recorded cannon and recorded chimes. The din got a little heavy, particularly when the cannon were blasting away from speakers at the sides of the stage.