Of all the resignations announced by heads of this city's major musical institutions, Metropolitan Opera general director Bruce Crawford's, handed in last month, was the least expected.

The former chief executive officer of a leading Madison Avenue advertising firm seemed cozily ensconced in his position at the head of the Met, one he will have held for barely four years when he steps down April 1. Crawford took over an opera house in deep trouble both behind the scenes and on stage. He leaves a smoothly running bureaucracy and a roster that is finally beginning to welcome the European superstars back into its ranks.During his tenure, Crawford announced plans to produce opera in cooperation with the Brooklyn Academy of Music (BAM) at its theater in Brooklyn - a foretaste of the mini-Met he and music director James Levine still maintain is uppermost in the company's priorities. The Met commissioned Philip Glass for a new opera and finally scheduled John Corigliano's Beaumarchais opera, which it had commissioned for its centennial season (1983-84).

Crawford put a brave face on the Met's seemingly insoluble problem: Seven shows a week, nearly eight months a year put insurmountable burdens on a repertory company, particularly now that Met fees are no longer competitive with European (which have long been insanely high thanks to elaborate government subsidies).

Therefore, he allowed major stars to come and sing a handful of performances, rather than stay with the production for its entire run, because he knew that without stars, no opera house can be called major. And last year, he achieved his greatest coup in luring conductor Carlos Kleiber to this house for four electrifying "Bohemes."

Nevertheless, despite Crawford's efforts, casting continues to be the Met's artistic dilemma. Some nights the problem is with singers not right for their parts; other nights it's the conductor who saves or sabotages the performance. The most serious example of the latter came when Alessandro Siciliani made his debut conducting the popular double bill of Mascagni's "Cavalleria Rusticana" and Leoncavallo's "Pagliacci" (known familiarly as "Cav-Pag"). Siciliani's eccentric, anti-singer performances at the New York City Opera indicated a conductor downright hostile to the human voice; at the Met, every time a singer was in trouble, he turned foe rather than friend, leaving experienced and inexperienced alike musically stranded. It was a stunning display of musical irresponsibility.

Speaking of debuts, there have been at least 12 in the past six weeks. Of those I covered, the most effective, finally, was Lucia Aliberti's as Lucia di Lammermoor. Aliberti seemed consciously to imitate Maria Callas, yet her performance had enough moments of grandeur and imaginative interpretation to make one hope she will become her own artist, rather than an uneven clone of a vocally flawed legend. She worked well with her Edgardo, veteran tenor Carlo Bergonzi, who occasionally suggested the grandeur that was once his to command.

Among the other debuts, only one other was a focal point of real interest: American Wagner-Strauss soprano Cheryl Studer as Micaela in Bizet's "Carmen." Her first act duet was lovely, but the big aria was forced and often out of tune.

The much-recorded Ilona Tokody made her debut as Nedda at the first "Pagliacci" and revealed an awkward stage presence and a soprano short on tonal allure. In the "Cavalleria," the two baritones who shared the role of Alfio were both making debuts: an over-emotive Bruno Pola with potent high notes, and an appropriately sinister but thin-voiced Alain Fondary.

Operatic staples continue to create terrible casting dilemmas at the Met. A routine performance of "Madama Butterfly" was sparked only by the conducting of Myung-Whun Chung - vibrant, nuanced, and refreshingly brisk of tempo.

A "Barbiere di Siviglia" with what looked to be a strong cast, turned out to be uncommonly dull. Even Kathleen Battle - a usually charming performer of the soubrette repertoire and often a delectable singer - whose Rosina sounded dwarfed by the house and by the role.

As mentioned, "Carmen" suffered from poor casting, and as for Placido Domingo's conducting, his major contribution was the restoration, for the first time in 16 years, of Ernest Guiraud's sung recitatives.

As for the "Cav-Pag" revival alluded to earlier, the first "Pag" was a dud, from Jan Pons's throttled-back singing of the "Prologo" to Ermano Mauro's hammy declaiming of the final "La commedia e finita." Curiously, Mauro was an unexpectedly fine Turridu in the "Cav." His Santuzza was Ghena Dimitrova, a robust singer with a huge voice which she used to telling effect throughout the grueling stretch of this demanding role.

And when Giuseppe Giacomini assumed the role of Canio at later performances of "Pag," the Met really was the Met for a glorious moment. Giacomini was vocally magnificent - a huge focused trumpet of a tenor suffusing all the lines with the sort of ringing, yet seemingly effortless outpouring of tone one has all too rarely heard in opera these days. If this is the sort of performance Crawford has striven to inject when possible, his impact will have to be considered ample.