SCHENECTADY — Bass-baritone William Powers has sung hundreds of roles over a 30-year international operatic career, but none gives him such pleasure as the role of the rapacious Scarpia in Puccini’s “Tosca.”

“I wrote the part,” Powers said from his home in Illinois during a break from tour. “When I go onstage, I cease to be William Powers.”

On Wednesday, he’ll sing the role when Teatro Lirico D’Europa presents “Tosca” at Proctors. Some of Powers’ other roles can be heard on his solo CD, “Rogues and Villains,” and “The Worst of William Powers” (both on Centaur).

The opera is based on Victorien Sardou’s play “La Tosca,” written for Sarah Bernhardt. Giacomo Puccini saw the play and immediately realized it had great potential as an opera. He hired Luigi Illica and Giuseppe Giacosa to write a libretto, and in 1900 the three-act opera premiered. Although criticized at the time for excessive brutality, the opera has become one of the world’s favorites.

The opera is set in 1800 in Rome when there was bitter political intrigue between Bonapartists and the monarchists. Angelotti, a consul of the short-lived Roman republic who has escaped from prison, takes refuge in a church where his sister, a beautiful blue-eyed blonde, has left him women’s clothes to aid his escape.

Cavaradossi, a politically liberal painter and friend of Angelotti, is also in the church, where he’s painting a picture that looks like the sister. Angelotti reveals his presence only to hide again as Cavaradossi’s mistress, the singer Tosca, enters and jealously questions Cavaradossi about the woman in the painting.

Tosca leaves and Cavaradossi helps Angelotti to escape. Scarpia, the chief of police who is hot on Angelotti’s trail, enters. He recognizes the woman in the painting and suspects that Angelotti has gone off with Cavaradossi. Tosca returns and Scarpia, who has long coveted her, manipulates her jealousy to send her off, followed by one of his officers, to look for Cavaradossi and the blonde.

In Act 2, Scarpia rules the day. Cavaradossi is captured, tortured and then taken away to prison. He could be released if Tosca becomes Scarpia’s. She reluctantly agrees and asks for safe passage out of the city for Cavaradossi and herself, but Scarpia says a mock execution must be held to keep up appearances. As he stamps the passports, she stabs him to death.

In Act 3 as Cavaradossi awaits his execution by firing squad on the prison’s roof, Tosca arrives with his safe passage and tells him she killed Scarpia and that the soldiers will fire blanks. Alas, the bullets are real and Cavaradossi dies. Soldiers arrive to avenge Scarpia’s death but Tosca hurls herself over the parapet to her death.

Villain as focus

Although Scarpia is dead by the end of Act 2, Powers said the character is really the focus of the opera, which is why Puccini made him a bass-baritone.

“We’re always the villains,” Powers said. “A low voice commands authority.”

Puccini didn’t stint on the musical difficulties, either.

“It has a difficult range. It takes you to the ultimate ends,” Powers said.

What makes for greater difficulty is that Powers is singing the majority of the tour’s 31 performances of “Tosca.” This has involved crisscrossing the country from one night to the next, often in different states.

“It’s monstrous travel,” Powers said.

It’s not that Powers hasn’t done tours before. Twenty years ago when he toured with Boris Goldovsky, performances were usually clustered or in a specific section of the country. But Teatro Lirico, which is the only opera company touring these days, does a 20-performance fall tour and a 48-performance winter tour that involves performing several different operas in venues all over the United States. Musicians and chorus members travel by bus while some of the stars fly longer distances. But on one set of performances in February that involved going from Missouri to Illinois to Iowa in a three-day span, Powers decided he couldn’t deal with being on the bus through the winter weather.

“So I rented a car and drove the six hours and waited for the poor devils who showed up looking out the bus’s window,” he said. “Sometimes, it’s good to be king.”

Strict discipline

Powers’ strict discipline keeps him from worrying about his voice if he has to sing every night.

“I have an extraordinary, rock-solid technique,” Powers said. “But I’m paranoid about the vagaries of travel or getting flu. I take a lot of vitamin C. I’m locked into a state of preparedness.”

To stay fresh, he reviews each night’s performance to determine if his posture was the right one to covey his emotions, if he responded well to one of the four sopranos hired to sing the role of Tosca and whether he could do anything better or add another wrinkle to the role. The opera, he said, is the ultimate in a dramatic opera. So he feels he must always walk a tightrope emotionally. When Teatro’s director Giorgio Lalov hired him, Lalov asked if he’d sung the role before. But he didn’t give Powers any stage direction.

When he sings his last Scarpia on tour March 20 in Palm Beach (the tour ends March 23 in Atlanta), Powers will head home to renovate his house over the summer. The hope is to sell it so he and the family can move to Paris, where it will be easier to fulfill his European operatic obligations.

“My career is cranked,” he said. “I’m still unstoppable.”