Verdi operas on CDs show variety in conductors' approaches. Sets vary in amount of fidelity to score and composer's intent

There was a time when performing early and middle-period Verdi operas was a fairly simple matter: Singers who had the high notes were allowed to interpolate, i.e., add a harmonically complementary higher note to the one in the score.

Repeat verses of arias were eliminated, as were some incidental moments throughout the score - a musical process known as cutting.

And the raw, energy of the musical lines in these sometimes elemental but always stirring works was never allowed to lapse.

These days a new breed of conductor is in charge of opera, one that frowns on interpolations, even when they clearly enhance the dramatic thrust, one that restores or ``opens up'' all the cuts, even when the music is poor or when the momentum of an act or scene will be impaired.

These conductors also favor a dogged fidelity to the printed score over the spirit and intention of the composer - as if merely getting the notes out with the appropriate (and rigid) attention to dynamics, accents, and tempo was the only thing necessary to bring any opera score to life.

What emerges is a listless performance of a vital work. For instance, in the EMI/Angel recording of ``Ernani'' (just recently transferred to three CDs, set number CDCC 47082), conductor Riccardo Muti crosses all the ``t's,'' dots all the ``i's,'' opens all the cuts, bans all interpolations, and turns a fun opera into a dull one. On a practical level, with all those cuts opened, the role of Elvira becomes a marathon of high ``B's'' and ``C's.''

There is an insistent energy to Mr. Muti's brusque reading, but the performance is wanting in majesty and dramatic insight. Pl'acido Domingo lacks the heroic ringing top notes to bring the impassioned title role to life; Renato Bruson has never had the top notes, the robustness of voice, or dynamic musical personality to do justice to the role of Don Carlo; Nicolai Ghiaurov, the Silva, sounds tired and frayed of voice. Verdi's `Attila'

Another recent conversion to CD is the Philips recording of ``Attila'' (412 875-2, two CDs), a 14-year-old performance with Ruggero Raimondi in the title role. This was part of an early-Verdi cycle conducted by Lamberto Gardelli, whose tepid, listless conducting throughout seemed to indicate he had forgotten that these inflammatory operas incited riots in the theaters. Here, Mr. Raimondi creates a vivid character; Sherrill Milnes sings a good robust Ezio; and Dutch soprano Cristina Deutekom was cast because Philips is a Dutch company. The set's real merit is Carlo Bergonzi's magnificent Foresto. The transfers to CD only enhance what was a sonically handsome set. `Rigoletto' on DG, Philips, and London

Nowhere are the differences in performance style as pronounced as in ``Rigoletto,'' three recordings of which are now available on CD. The work is a supreme singer's piece and a major piece of drama as well. To deny the singers their full glory robs the work of true excitement. Yet to turn it into mere vocal exhibition saps it of dramatic richness.

For me, the best stereo ``Rigoletto'' is conducted by the veteran Italian maestro Carlo Maria Giulini, now superbly transferred to two CDs (Deutsche Grammophon 415 288-2). He finds a dark, Shakespearean quality to the work, and the Vienna Philharmonic gives him all the burnished colors and searingly intense playing he demands. He has opened all the cuts and has also allowed his singers several of the traditional interpolations, because he knows those notes enhance the drama of the moment when effectively done. Nevertheless, in other places, he eschews those traditions, thereby tightening the thrust of the musical action. Throughout there is the sense of a major musical exploration that reveals Verdi's innermost meanings.

Piero Cappuccilli's eloquently sung Jester is a thing of great constrasts - hate, love, tenderness, cruelty. The Duke is Pl'acido Domingo in one of his better recorded performances in opera. Ileana Cotrubas is a true lyric-soprano Gilda, affecting, fragile, yet capable of suggesting the resolve that leads to her sacrifice her life to save the caddish Duke. Nicolai Ghiaurov's Sparafucile is especially menacing, and Kurt Moll's Monterone and Elena Obraztsova's Maddalena are lavish casting turns indeed.

A quick listen to the last act of conductor Giuseppe Sinopoli's new recording (Philips digital two CDs, 412 592-2) will tell the listener all he or she needs to know: Sinopoli imposes aribtrary tempos and abrupt changes, and refuses all interpolated notes. In a word, he feels that sticking to most of the recent findings printed in the new critical edition of the score (though this recording is not listed as being of that edition) is enough to bring the work to life. Unlike Muti, Mr. Sinopoli occasionally gives his singers room to expand into a long arching phrase, and he does allow singers moments of sheer vocal splendor, albeit without interpolations.

Renato Bruson has always lacked the quality high notes a ``traditional'' Rigoletto demanded. Here he is allowed to ignore them, but his performance falls short - a musicianly but dramatically and vocally lightweight Jester.

Neil Shicoff's Duke does not capture his distinctive tenor voice in peak form. Brigitte Fassbaender is an adequate Maddalena, and Robert Lloyd a sonorous Sparafucile.

Finally, the Gilda, Edita Gruberova, is a mistress of the stratosphere denied her soaring moments of glory. She makes her mark nonetheless in her vivid portrayal.

On the handsomely engineered London ``Rigoletto'' (two analog CDs, 414 269-2), Joan Sutherland is the full-voiced Gilda with a dramatic coloratura that has the extension for the interpolations she inserts, as well as the vocal size to ride the considerable climaxes of several scenes. Though she gives a dramatically cool performance, her gloriously sung Gilda is one of the principal reasons for owning the set.

The other reason is Luciano Pavarotti's dashing Duke; he and Miss Sutherland work particularly well together. Martti Talvela is the earnest Sparafucile. Sherrill Milnes has his share of rough moments in the title role, and conductor Richard Bonynge is content to give a lyrical, rather low-key, singer-oriented performance.

Ironically, this vocally impressive ``Rigoletto'' proves that just singing the opera well is not enough to bring forth all its dramatic possibilities.