By the time all the dominoes stopped falling after Natalia Makarova's injury Saturday night at the Kennedy Center, a new conductor was in the pit for yesterday's matinee performance of "The Turn of the Screw" in the Terrace Theater. He is David Abell, a young apprentice conductor who is working with John Mauceri. Mauceri, who is music director for "On Your Toes" as well as the regular conductor of "The Turn of the Screw," was caught up in emergency work yesterday afternoon, keeping the Broadway show on its toes.

As assistant to Mauceri, Abell has been busy with rehearsals for the Britten opera, and that experience paid off unexpectedly yesterday (at least in Act I, after which I had to leave for another assignment). In terms of visibility, it was not as spectacular an event as the substitution of a leading lady (Martha Senn in "Carmen" and Olivia Stapp in "Tosca," so far this season), but it is a more demanding assignment and it was crucial for the total impact of yesterday's performance -- its pace, the balance of instruments and voices, the accentuation of the music and the total atmosphere, which is derived largely from the orchestral interludes and obbligatos in this opera.

As might be expected when an apprentice fills in, Abell did not depart spectacularly from the style established by Mauceri. What he did instead was to fill in for his mentor so expertly that it was hard to tell that this was a very young conductor making his professional debut.

Professionalism is what he delivered -- quiet competence, economy of gestures, precision of nuance. The phrasing was as crisp, dramatic and authoritative as it had been on opening night, and the dramatic impact was even more shattering. This production has shaped up extremely well in repeat performances; opening-night problems (which were minor in any case) have been skillfully overcome and it is now a vintage interpretation of an intriguing work of art. This improvement is clearly an ensemble effort, not a result of Abell's conducting in one performance. But the improvement could be heard quite clearly under his direction yesterday.