Nabucco with the Auckland Philharmonia Orchestra

Helen Medlyn is excited by her role as the daughter of the king in Verdi's Nabucco. Photo / Richard Robinson

Helen Medlyn has little regard for barriers when it comes to singing. You may have heard her in Messiah, on the operatic stage or dishing out cabaret captivation with pianist Penny Dodd. Most recently, in Auckland, she triumphed singing Gillian Whitehead's Alice with the New Zealand Symphony Orchestra.

The 30-minute monodrama was written for and premiered by Medlyn in 2003.

She remembers "going to Gillian's little flat in Mt Eden and this amazing woman asking me how I felt with this or that phrase. I felt part of the evolution of the work."

Alice is a big sing and she admits that the first performance was nerve-wracking. "Since then I've done some Mahler and it helps with the storytelling," she points out.

"I was able to push my danger limits a little further, especially with the spoken stuff. I really enjoyed being the horrible mother and sister, as opposed to the gentle Alice with that core of steel inside her."

Next Friday Medlyn takes part in Auckland Philharmonia Orchestra's Nabucco, this year's Westpac Opera. The mezzo was a ferocious Herodias in the APO's 2008 Salome and a marvellous sparring partner for the late Elizabeth Connell in 2010's Elektra. Conductor for both was Eckehard Stier who is also at the helm for Friday's Nabucco.

"Eckehard works organically and I like that," Medlyn beams.

"He's not dictatorial; you're allowed your own space and to have some input."

Nabucco may be billed as a concert performance but, with singers not using scores, Medlyn will have the opportunity to present her character in the round, alongside the celebrated American baritone Sebastian Catana and Italian soprano Paoletta Marrocu.

Nabucco is early Verdi, written in 1842, a decade before the trifecta of Rigoletto, Trovatore and Traviata. Its tale of the plight of dispossessed Israelites in Babylon, underlined with fervent choruses, struck a chord with Italian political sentiments at the time. Medlyn plays Fenena, one of the daughters of Nabucco, the Babylonian king.

The character is very much caught up in the opera's political business and Medlyn is chuffed, just for once, to be playing a princess.

"There's a beauty of soul in Fenena that I really love," she says. "Not that I didn't enjoy being the Wicked Witch of the West in The Wizard of Oz last year or the Old Lady in Candide last month in Wellington."

Growing up in West Auckland with a father she describes as "a Wagner and Verdi nut", it is little surprise that Nabucco's composer is one of Medlyn's favourites.

"The passion is so potently and patently there; there's no pussyfooting about," she enthuses. "I love Mozart but I really adore Verdi because he grabs you by the scruff of the neck and throws you round the room."

Her big aria, Oh, dischiuso, e il firmamento is "so beautiful," she sighs. "Fenena is going to die with dignity and sings this sweet, sweet song for the heavens to open up for her. It's so gentle and different from anything else I've done," she laughs. "I can't whack it out. It's got to be reflective."

Though Verdi's opera is celebrated for its choruses, especially the famous lament of the Hebrew slaves, there is also some great ensemble work, which Medlyn particularly enjoys.

"Verdi was so clever with his palette, putting the colour of your voice against others so it creates this amazing sound picture," she says. "You're allowed your moment of brightness and being looked at by the audience; then you have to fade away before you come back again. I like that give and take."

What: Nabucco with the Auckland Philharmonia Orchestra
Where and when: Auckland Town Hall, Friday at 7.30pm