By Belinda Goldsmith

NEW YORK (Reuters Life!) - American baritone Nathan Gunn, whose chiseled physique has won him as much attention as his warm voice, says it's no longer enough for opera singers to be able to sing well -- they need to look good, too.

Gunn said opera has, much like the rest of culture, become more focused on beauty, with opera companies starting to use their stars' looks in marketing campaigns to entice audiences.

"Opera is visual and not just to be listened to. Looks count," Gunn, 36, told Reuters in an interview.

"There is a much larger pool of talent out there now. The Metropolitan Opera House -- if they are going to consider themselves the greatest opera house in the world -- wants to hire the greatest singers and performers. They will choose the best fit that they can."

Gunn is part of a new generation of performers, including Russian soprano Anna Netrebko, British soprano Kate Royal and Peruvian tenor Juan Diego Florez, who have helped fuel a debate about the physical attributes of opera singers.

After decades in which little attention was paid to opera singers' age, size or appearance, a trend has emerged for vocalists to look the part.

The issue came to the fore in 2004 when American soprano Deborah Voigt was released from an engagement at Covent Garden because she couldn't fit into a dress. She has since undergone gastric bypass surgery and lost about 135 pounds.

Classically trained singers like the quartet Amici Forever, operatic pop vocal group Il Divo, and Welsh mezzo-soprano Katherine Jenkins have had great chart success with their crossover genre coupled with their good looks.

These popular acts are not viewed as true opera singers by many hard-core opera devotees, but stars like Gunn are also putting greater emphasis on looks to broaden the appeal of their genre.

Gunn, who has appeared in many of the world's most prestigious opera houses, including the Metropolitan Opera, Royal Opera House and Paris Opera, says he stays fit by keeping up with five young children, riding motorbikes and practicing martial arts.

He has no qualms about stripping to the waist on stage if it makes sense for the production.

"For me, keeping opera, keeping musical theater, out of the museum is important," said Gunn, who this week released an album of romantic songs called "Just Before Sunrise."

Gunn, who grew up in South Bend, Indiana, began singing in high school and studied music at the University of Illinois.

After winning the Metropolitan Opera's National Council Auditions in 1994 he joined the Met's young-artist program and has since been booked up with recitals, orchestras and operas, currently planning his 2012 season.

In September Gunn will perform in the Metropolitan Opera's production of "Romeo & Juliet."