It's a testament to how busy Idina Menzel has been that the only time she's free for a chat comes when she's in a taxi on the way to the airport for a holiday.

 

The prospect of fitting in another work obligation prior to a break might make a few folk groan, but Menzel is in relaxed mode, and it's no wonder she fancies a few days off.

The past year has brought a Broadway run in new musical If/Then, a Christmas CD released at the end of 2014, a run of her own shows, and the extra fame that's come her way for voicing Elsa in Frozen, the Disney film that became a commercial and pop culture juggernaut.

"You do recognise that you're in something that feels magnetic and special, and it moves you," says Menzel, discussing her most famous roles ahead of a Glasgow show on Wednesday night.

"You never know that it's going to be a sort of phenomenon, you just surround yourself with more creative and intelligent people, and hope for the best! Thankfully once every decade I've had something like this that's really helped my career."

Indeed, Menzel's career has seen her thrice bitten when it comes to juicy parts. In 1996 she landed her first taste of fame in Rent, where she played Maureen, a role she later reprised in the film version.

A decade later she went green to play the misunderstood witch Elphaba in the smash-hit musical Wicked, winning a Tony Award in the process, and that was followed by Frozen and an Oscar for the ubiquitous Let It Go.

Her defining roles also suggest a tendency for Menzel to gravitate to playing misunderstood outsiders.

"I feel very proud of it, and quite a responsibility, actually, to the young people that have connected with these characters," adds Menzel.

"It's a gift, but I need to practice what I preach and be aware of being a role model to kids in the crowd. These characters remind me of what I need to learn in life, too, particularly about self-esteem and confidence, and my own need as a woman to embrace what makes me different."

For all that Menzel has enjoyed huge success in recent years, her path was not always a smooth ride. She worked as a wedding singer while studying at the Tisch School of the Arts in New York, before landing her role in Rent, but a record deal and solo album didn't work out for her.

Even now, as a hugely in demand singer, she admits that she can doubt herself, which is partly why she relates to empowerment anthems like Let It Go and Defying Gravity so much.

"I'm just like everyone else, I have good days and bad days," she says.

"There's days when it's easier to get out there and not care what people think, and then there's others when it's more complicated and you have to build yourself up.

That's why I consider singing these songs an incredible gift, because not only are they beautiful and connect with other people, but they remind me what I want to be."

Those songs will unquestionably feature in her Glasgow set tonight, but it's not just a run-through of musical hits and solo material. She's intending to drop in a few covers, too.

"I usually pick covers where I can give an interesting interpretation. There's a mash-up of Roxanne and Cole Porter's Love For Sale, so that's my streetwalker medley, and I like to explore different ways to express myself onstage.

"It's an opportunity to show a different side to me - I'm a fan of Radiohead and Creep in particular, so I'm always keen to sing it."

A Frozen sequel has already been greenlit, but Menzel seems unlikely be lured to Hollywood permanently. A national tour of If/Then will follow later this year, and the theatre clearly remains her most comfortable stage.

"Theatre's my first love. I include live performances like concerts in that, and going on stage and trying to connect with people and an audience, knowing that every night will be a little bit different.

"I love the camaraderie in the theatre. It's where I feel most myself."

Idina Menzel plays the Royal Concert Hall tonight.