MARILYN HORNE is sitting on her sister-in-law's couch here, trying to articulate what 35 years as a top-rank diva have added up to. But it's written all over her face: satisfaction and a bubbly effusiveness that an hour's interview will show is but one manifestation of an inner radiance nurtured by a life in music. ``At least I don't think I've been on an ego trip all this time,'' she says, laughing and sipping tea from fine bone china. She has been on a program of calisthenics and aerobics to increase stamina on the stage. She needed the energy for her four performances here of Rossini's ``Tancredi,'' a dramatically and musically demanding role she has put her stamp on from Chicago to Houston to Venice.
``Look, you have to have a lot of self-esteem to put one foot in front of the other and walk out there virtually naked and say to an audience, `This is all I know, all I can do.'''
But for soprano Horne, the driving force behind jetting across the United States and Europe - at the pace of 50 performances a year - is the music. ``I feel through it a kind of spirituality, the only communication with `whatever is out there' [that] I don't feel any other time, except when I admire nature.''
Miss Horne adds, ``It's no secret that anyone with 3 decades in professional opera is not looking forward to many new roles.'' She is looking forward to new music in the recital venue, however, with 1,400 recital performances behind her and ``still a greediness about wanting to learn more. You could never scratch the surface of what's out there, in an entire career,'' she says.
After growing up in California and debuting at age 20, she began garnering accolades that have never stopped. ``In Miss Horne's hands - or rather her beautiful voice, sensitive face and tremendous gifts as an actress - lies a good portion of the future of American opera,'' wrote the San Francisco Chronicle after her major American operatic debut in 1960, ``and its future is therefore bright indeed.''
More recently she became the only living artist selected by Harold Schonberg for his New York Times list of the nine ``all-time, all-star singers in the Met's 100 years.'' And in 1987, the National Society of Arts and Letters gave her its highest award of merit for lifetime achievement.
She will talk about the present and future of American opera - one that has grown astronomically from the mere five companies that existed when she began. But first, Rossini and his rarely performed ``Tancredi,'' which represents her first operatic performances here in 23 years.
``The three principal roles are excruciatingly hard to sing,'' she says of the bel canto (lyric singing, in which beauty outweighs emotion) style that went out by the end of the 19th century and was brought back in a minor renaissance by Maria Callas. She has performed the romantic/tragic role - conceived by Rossini at age 21 - about 50 times, and says, ``It demands everything of a singer that can be done vocally.'' The role began for her in 1977, when Philip Gossett, a friend and scholar, restored a less upbeat ending.
``It really brings a totality to the opera that the happy ending didn't,'' says Horne. ``And the end is a real surprise for the audience - written in the grand style of Handel and Gluck. It is not at all the Rossini we know in `The Barber of Seville' and `Italiana Nargeri.'''
Her former husband, Henry Lewis, was conducting the Los Angeles Chamber Orchestra and Los Angeles Master Chorale for ``Tancredi'' here. ``To say he has really brought the piece to life in a way no one else has is really sticking my neck out,'' says Horne, ``because I've sung it with a lot of other great conductors.'' A leading Italian journal has said,``among the great Rossinian interpreters of the world, she is the greatest. No one can rival her in trills, range, color, brilliance, legato, articulation, or dynamics.''
Though she has, of late, been occasionally criticized for singing without heart or with too much chest for dramatic effect, she is still known for her supreme confidence onstage. At least one critic has said she could sing another decade with powers undiminished, but Horne isn't making plans beyond another five years.
The dynamics of today's opera world are dictated increasingly by the demands of recordings, radio, and television, she laments. ``Now, we are inundated with media [demands], so everyone is jockeying to make sure his or her opera is going to get telecast or recorded, which has made horrendous inroads into performance practices.'' By that she means that all other projects play second fiddle in time, attention, and investment.
She says, nevertheless, that she is as big a culprit as anyone else. ``I'm of two minds about it, because I want the opera to get out to millions instead of thousands, but I also regret the fact that they can't see it in its true form.''
She says opera singers were not meant to be seen close up ``with a lens'' and abhors the casting of operas for physical characteristics. ``With a few great exceptions, it is getting down to physical type, I hear it all the time.''
Two other worries of Horne concern miking and sets. ``Acoustic enhancement will be the death of good singing when it comes, just like it was to good singing on Broadway,'' she says, adding, ``notice I say `when,' not `if.''' And on the attention and money spent on elaborate sets: ``I see red when I see an opera advertised as `David Hockney's ``Tristan und Isolde''' or `Peter Sellars's ``Tannh"auser,''''' she says. ``Dramatics cannot supersede the singing; they have to go hand in hand.''
She hesitates to comment on a general trend, criticized by some, of fewer good singers and fewer audiences that can discriminate between good and bad.
``Audiences don't necessarily know when they have heard something mediocre, but they sure know when they've heard something good,'' she says.
Part of the problems with opera are the same as those with classical music in general, she says, one symptom of which is conductors who hold down three jobs at once. ``With notable exceptions of James Levine [and] Henry Lewis..., [conductors] don't spend time with their singers anymore.''
A role in music education is one she sees for herself in the future, but she is not sure where or when. ``I was asked by my friend Jerome Hines to head up the voice department of a wonderful new school in New Jersey,'' she says. At first she accepted, then found she didn't have enough time. ``Teaching is very difficult ... to attempt while still doing opera - and I'm not out of that ... yet.''