HOW do you get through performing an opera that is on the high side of five hours? When it comes to Wagner, tea helps, Christine Goerke suggests.

“Gotterdammerung is long. It’s a huge thing,” the American soprano admits. “But there are scenes. And you do your big scene and then you go off and have a cup of tea. And then you come back and do another big scene. And you go and have another cup of tea. And you do this until you get to the end when you have something stronger than a cup of tea.”

Ah, right, and what might that be, Christine? “It’s always whisky or bourbon. It just depends on where I am.”

Right now, Goerke is back in Edinburgh for the aforementioned Gotterdammerung, the culmination of Wagner’s Ring Cycle at the Edinburgh International Festival, performed by the Royal Scottish National Orchestra under the leadership of Sir Andrew Davis. Goerke will take on the role of Brunnhilde.

Originally from Long Island, New York, Goerke has performed at La Scala, the Royal Opera House in London and the Met in New York, but she is thrilled to be back in Edinburgh. These days, she is very much the go-to soprano for what she delightfully calls the “big girl” roles. And there are few bigger than Wagner’s Brunnhilde.

How would she sum up Brunnhilde? “Which one? That’s the thing. She is the most complete character that I have sung. That I will ever sing. I find her fascinating, music aside. She goes through a huge transformation. She is the wily teen. She sees her father fall off the pedestal that she put him on.

“She learns the lesson and it’s very difficult and she takes another chance on caring about somebody and that doesn’t work out well for her either. By the time she gets to the end of the entire cycle she becomes the hero that is needed at that moment.”

She becomes a badass? “She is completely and utterly badass, yes.”

Perhaps it was inevitable that Goerke would end up playing the part. “When I was starting to get into the ‘big girl roles’ I thought my first step should be Sieglinde and I understudied a few times. I never got to sing it. But I pushed very hard to do it at one point, and the director who knew me very well said: ‘You should not sing Sieglinde. You’re Brunnhilde. I know your relationship with your father.’”

How so? As a teenager, Goerke says, she butted heads with her own father constantly. “We have a very good relationship now. I’m fiery. I do not hold my tongue. If something bothers me, I say so. And if I see someone not being treated well, the mommy in me speaks up for them.”

Even in a short conversation you can get a sense of the scale of Goerke’s personality. Which makes her well suited to the Ring Cycle. “I love Wagner, I love Strauss. There’s something about the harmonic language of the German music in that period that speaks to me.”

The fact that we get to her hear singing it at all could be regarded as a bonus. In the early years of the 2000s Goerke almost gave up on opera when she began to struggle with her voice. “I was singing Handel, and it should have been a walk in the park for me. That was my wheelhouse. And it just wasn’t working. I couldn’t get the support underneath me. My coloratura wasn’t working and I literally had no idea what was wrong.

“I almost quit singing. I had those thoughts for six months and luckily some smarter friends talked me out of that, and I went and got a new teacher.

“It turned out my voice had been growing faster than I had expected it to and, little by little, unconsciously, I had come away from my support. And so, I wasn’t connected to my body. I was singing in such a way that everything was really tight, and I was terrified. And it was as simple as reconnecting to my body and realising it was time to change repertoire.”

In short, it was time to move to those big girl roles. And there are none bigger than Brunnhilde. What she loves about Wagner is the way the text and the music stand on their own, she says.

“It doesn’t take a lot of fancy sets. It doesn’t take fancy costumes. It takes commitment to the art.”

But you’re going to have a costume for Edinburgh, aren’t you? “Well, I’m not going to go out there in my jeans ... Unless they let me.”

Gotterdammerung is at the Usher Hall on Sunday beginning at 4pm and running for six hours, 25 minutes, including two intervals. Visit eif.co.uk.