"The Sound of Music" has never sounded better than it does in an opulent New York City Opera revival with Debby Boone in the starring Mary Martin-Julie Andrews role.

The production has been co-produced by theatrical producer James M. Nederlander with an eye to a national tour or a move to Broadway after its limited run at the New York State Theater ends April 22.Whatever its future, this show mixing Broadway talents with opera company singers is definitely of Broadway caliber.

"The Sound of Music" was a runaway success when it opened at the Lunt-Fontanne Theater in 1959 for a three-year stay, extensive tours and overseas productions. The 1965 film version held the record for top grossing musical for years and is a television favorite. It was last revived here at the New York City Center in 1967.

It was never a favorite of theater hard-liners, who found Richard Rodgers and Oscar Hammerstein II's Austrian version of "The King and I" overly sentimental.

Hammerstein's son, James, has directed this revival so adroitly that it avoids even a hint of bathos while still evoking an occasional tear from the audience.

Award-winning pop singer Boone as Maria Rainer, the governess who marries her aristocratic boss and acquires a ready-made family of seven children, is a real surprise, although this is her third appearance in a company of "The Sound of Music."

She has a luminous personality, not unlike Andrews', a fresh soprano voice, a touch of tomboy and a charming vulnerability that Mary Martin lacked in the role.

Boone's performance is strong enough never to be upstaged by the children, those notorious stealers of scenes. She seems at times to be simply their eldest sister.

Boone also plays well opposite Broadway veteran Laurence Guittard as Capt. Georg von Trapp, the anti-Nazi she marries on the eve of their flight to Switzerland.

Guittard is not as authoritarian as Theodore Bikel was in the original production, lending the role an attractive sensitivity and a fine if not strong baritone voice.

Werner Klemperer scores with the audience as the amusing, urbanely manipulative impresario who melds the Von Trapps into a choral ensemble that historically brought them to the attention of the Western world and Rodgers & Hammerstein. He does what little singing the role requires adequately.

One of the strengths of this production is the beautifully conceived Mother Abbess of Claudia Cummings, a New York City Opera soprano. She handles the role, and Maria, a onetime postulant at her abbey, with conviction, giving the plot a reality that this Cinderella story may not have had otherwise.

Cummings brings both acts of the musical to a thrilling climax with "Climb Every Mountain," a song without match in Rodgers & Hammerstein repertory with the exception of "You'll Never Walk Alone" from "Carousel."

Others who turn in fine peformances are Marianne Tatum as the rich Viennese widow who charms Von Trapp for a time, Marc Heller as as a nice young man turned Nazi who has a flirtation with the eldest Von Trapp girl, pertly played and sung by Emily Loesser, Ellen Tovatt as the Von Trapp housekeeper and David Rae Smith as the butler.

Neil Peter Jampolis's tasteful sets and impeccable lighting lift "The Sound of Music" above the level of City Opera's four previous spring musical comedy productions paid for by a $5 million grant from the late Mae and Lawrence Wien. This is the fifth and last of the series.

The reception hall of the Von Trapp schloss is a lyric summation of the baroque style, and the schloss' terrace with distant mountain views conjure up a leisurely lifestyle soon to be doomed by war. The abbey scenes are deliciously detailed, especially the gilded altar screen set against an ornateretable mural depicting a convolution of angels singing the gloria.

Suzanne Mess' costumes are delicious, especially the children's.

Credit goes to conductor Richard Parrinello, making his debut with the opera company, for a lively reading of a lovely score, which contains such standards as the title song, "My Favorite Things," "Do Re Mi," "Sixteen Going on Seventeen" and "Edelweiss."