In Mr. Norrington's case, he said he had experimented with all the metronome markings in all nine Beethoven symphonies and found every one of them convincing with a single exception - that tenorial march in the Ninth, marked at a dotted quarter equals 84, which he felt to be slightly too slow.

Not everyone would agree with him in all these cases: the blistering pace of the double-bass recitative at the beginning of the last movement of the Ninth really did sound like human voices in hot spoken argument, but was so much quicker than what anyone else has done as to call awkward attention to itself. But as a rule, Mr. Norrington's performances make a bracing case that Beethoven was hardly so off base with his metronome as so many intervening interpreters would have had us believe. Rethinking Toscanini

Speaking of intervening interpreters, Mr. Norrington's Beethoven weekend made one think of two very different Beethoven conductors of earlier in this century. One was Arturo Toscanini, whose Beethoven -the last recordings especially, with the NBC Symphony - were cherished by his admirers during his lifetime but have since been widely dismissed as impossibly quick and inflexible.

Mr. Norrington's performances make Toscanini sound like a particularly acute anticipator of the early-music movement. In fact, his tempos come closer as a general rule than those of any other mainstream conductor to the composer's metronome markings. Even his habit of letting the brass punch aggressively through the string texture, regarded as a mannerism during his lifetime, now sounds like the wind-and-brass-heavy balances that obtain with original instruments.

Toscanini's champions stressed how he was merely the humble servant of the scores. Since then, Toscanini's style has more frequently been regarded as a subjective expression of his own hot, driven personality, and discounted as such. But maybe, at least in Beethoven's case, he was being more faithful to the composer than even some of his admirers realized. Recalling Klemperer

The other famous Beethoven conductor of yesteryear to come to mind was Otto Klemperer. Mr. Norrington is a darling of the English musical press these days, as - in a very different way - Klemperer was during his years in the 1960's as a grand old man. But Klemperer was one archetype of the entropy of tempo - his Beethoven was glacial, weighty, inexorable where Mr. Norrington's (and Toscanini's) is brisk, bright and brilliant.