Karen Cargill looks ahead to pivotal 2015

Every night during that run, immediately before the curtain went up, she enacted the same preparatory ritual.

“I would stand in the middle of the big open set, and for just a few moments, with only the curtain between me and the audience, listen to the orchestra playing the overture. It was very important for me to have that special moment of being grateful for where I am, and to get ready to enjoy the experience,” the 39-year-old Arbroath-born singer explains.

Where Cargill is, is at the very top of her game. This was her second major Wagner role at the Met, the first being her highly-praised debut in 2013, when the New York Times singled out her eye-catching portrayal of Waltraute in Götterdämmerung.

Its critic wrote: “Karen Cargill brought such exquisite expression and a warm, vibrant and ample voice to the part that she thoroughly outclassed her colleagues onstage. Here, finally, was a singer who could control multiple dimensions, singing with fervent intensity without raising the volume and conjuring up different colours for her character’s pangs of pity, hope and anger.”

Critics here have been saying much the same about her regular appearances at the Edinburgh International Festival, at the BBC Proms, in her role in last summer’s Royal Opera House production of Richard Strauss’s Ariadne of Naxos, and more especially as associate artist with conductor Robin Ticciati and the Scottish Chamber Orchestra, an association that started with serialised Berlioz, and which has continued this season with the orchestral songs of Mahler.

In three weeks’ time, the current Mahler series resumes with the beautiful Das Lied von der Erde, for which Cargill teams up with tenor Stephen O’Neill. But before that she will complete a European tour with the London Symphony Orchestra, performing Mahler’s Fourth Symphony under Ticciati. In April, she’s in New York for another major milestone: her solo debut at the Carnegie Hall with long-term collaborator and accompanist Simon Heffer.

The pace is clearly hotting up. Before her most recent Met role, Cargill made her debut in October with the Cleveland Orchestra, again with Ticciati, resurrecting their golden interpretation of Berlioz’s Les nuits d’été. When I spoke to her in New York before Christmas, the memory was still very much alive. “Robin and I have done this music so often now it feels like a comfortable pair of slippers,” she says.

“But even when we were there in Cleveland, there is always that moment with the first song where you worry about how fast, how slow to take it. We both decided, we’ll just breathe and do it, because it’s the worry that makes things not settle.” It clearly worked. The Cleveland Plain Dealer critic described her performance as “ravishing”.

As Cargill prepares for a high-pressure 2015, it’s that new-found composure, she says, that will get her through it and help her produce the unique richness of sound and profundity of interpretation that is fast marking her out as one of the world’s leading mezzos.

Especially the Carnegie Hall debut. “Talk about fear”, she says, with her infectious, disarming giggle, betraying the delightfully modest personality of a woman whose priorities are divided between international stardom and family life in Bearsden with husband Nick and young son Adam.

“I had an epiphany about two years ago when I thought, you know, people just want to come and enjoy music and have a lovely evening. They want to see who you are, what you have to say. It’s obviously easier said than done, but that’s what I try to give them: to do the music justice and have fun with my friends.”

For her Carnegie programme, she’s chosen music that she and Heffer are completely comfortable with: all from the German Romantic tradition with songs by Grieg and Mahler, but especially those songs by both Gustav Mahler and his wife Alma Mahler that featured in a phenomenal CD they made last year. “This was such a discovery for us, to find that Alma was discouraged from composing by her insecure husband, yet when she finally did emerge as a composer, she wrote such beautiful songs,” Cargill explains. “You just wonder what she could have achieved had she been allowed.”

That’s just one major highlight in a year that will end in December with Cargill celebrating her 40th birthday. The rest of 2015 is a typical mixture of high-level operatic roles and concert work. “I’m not an opera singer or concert singer exclusively. I like to do lots of things,” she says.

That includes a new song cycle, written for her by Rory Boyle, with the Red Note Ensemble. Cargill will travel to Japan to appear in her first staged production of Berlioz’s Beatrice and Benedict under Seiji Ozawa. She has orchestra dates in Amsterdam, Montreal and Philadelphia, a solo recital in Washington as part of a wider American tour, another BBC Proms and returns to Covent Garden to revive last year’s success in Ariadne.

It’s the perfect balance and it comes at a time when her voice is in tip-top condition. “My voice has grown again, but it remains, as ever, a work in progress. Bizarrely, as things get busier, I’m discovering that singing is all about relaxation.

“I’ve been working on that with Dame Janet Baker, who, when giving me the best bit of advice when I was struggling with the emotional aspects of Mahler’s Kindertotenlieder, said ‘the angst is not for you. The angst was what the composer went through to put it down on the page. You just have to tell it. You’ve been given this gift. Just sing!’”

• Karen Cargill sings Mahler’s Das Lied von der Erde with the SCO at the Queen’s Hall, Edinburgh on 29 January and at City Halls, Glasgow, on 30 January.