NONFICTION : DIVO: GREAT TENORS, BARITONES AND BASSES DISCUSS THEIR ROLES by Helena Matheopoulos (Harper & Row: $25; 384 pp., illustrated).

Helena Matheopoulos has come up with a book of 22 interviews that will be of interest to vocal aficionados eager to savor the reflections of such current giants as Placido Domingo, Luciano Pavarotti, Carlo Bergonzi, Alfredo Kraus, Nicolai Gedda and Piero Cappuccilli. In some cases, most notably Bergonzi and Gedda, their opinions on favorite roles and interpretations are quite articulate.

However, the appellation “great” applied to such others as Giacomo Aragall, Jose Carreras, Thomas Allen, Simon Estes and Ruggero Raimondi leaves one wondering about Matheopoulos’ artistic yardsticks. Their inclusion as vocal paragons is a sad commentary on the state of singing today. Does anyone really want to know how Carreras, for example, rationalizes his abuse of a once-gorgeous lyric instrument?

Moreover, the author’s opinions, which come through in the interviews, seem shaped by the current standards of the British opera stage. She approvingly quotes Peter Jonas, English National Opera director, that the producer is the most important component in opera. She patronizingly dismisses such conductors as Tullio Serafin, Vittorio Gui and Antonino Votto as “old fashioned” and “glorified coaches.” These men merely had opera and its best traditions in their blood and knew how to impart their knowledge to generations of singers.

A stylishly sculpted Verdian phrase from a Bergonzi, who never could act, is always going to cause more excitement than a whiz-kid stage director. It is a pity Matheopoulos misses that point. It’s what opera is all about.