"So it's like Noises Off all over again, basically." Quinnell is talking about her role as Jessica in Alan Ayckbourn's Communicating Doors, one of three plays she appears in during this year's PFT season. This marks the sparkly eyed Welsh actress' return to the theatre after causing a stir during her last two stints here.

As opening gambits go, Quinnell's remarks on her costume – or lack of it – for her latest appearance is refreshingly, if somewhat disarmingly, candid, albeit utterly without guile. It wasn't just running round in her underwear as ditzy wannabe starlet Brooke in Michael Frayn's ingenious back and front stage farce that caused such a commotion. It was Quinnell's lively mix of a magnetic stage presence, instinctive comic timing and multi-tasking versatility in roles such as Eliza Doolittle in My Fair Lady, Lois Lane in Kiss Me Kate and Mabel Chiltern in An Ideal Husband that have captivated Pitlochry audiences.

Such a stir did Quinnell cause across her previous two seasons that she scooped the Leon Sinden Award, voted for by the audience, not once, but twice. In a two strikes and out approach that will allow her onstage colleagues a crack of the whip, Quinnell has been excluded from this season's voting.

"I think that's only fair," she says. "I just hope that I can vote for other actors in the company."

This season, as well as Jessica in Communicating Doors, Quinnell plays Mabel Chiltern in JM Barrie's Dear Brutus, and, in her third season-opening musical on the trot, appears as brutalised flower shop assistant Audrey in Little Shop of Horrors.

"It's quite surreal being eaten by a man-eating plant," Quinnell laughs, "but I get to play my clarinet and my sax, and it's a genre of music that I absolutely love: early rock'n'roll, Motown, doo-wop, you can't help but tap along. That's one of the great things about the musicals here. Because we're all playing instruments with each other onstage as well as acting, we're all relying on each other, and that gives things a real ensemble feel. Also, I get to do the four things I love doing most in life – singing, acting, playing my instruments and dancing – so I'm happy."

This isn't necessarily the case with the women Quinnell is playing. All of them, at least at the start of each play, are far from happy. Quinnell describes down-at-heel Audrey in Little Shop of Horrors as "The tart with a heart. Bless, she's stuck in a rut in skid row with the same job and an abusive relationship that she's too scared to get out of. It's quite sad, really. Beneath all the bright lights and colours it's really quite dark".

In the time-travel based Communicating Doors, Quinnell plays Jessica, a woman who is warned by a visitor from the future that the man she's just married will later murder her; while in Dear Brutus, she plays a woman whose husband is cheating on her, but who has the tables turned on her when they go for a walk in the woods.

While such a variety of roles will no doubt keep Quinnell on her toes, it is musical theatre that is both her natural habitat and her first love.

"I'd like to think I'm an all-rounder," she says, "because I loved doing Noises Off and An Ideal Husband as much as doing Kiss Me Kate. There's something about having a sing and a dance that just fills me with joy. I genuinely love it. I've only been playing the saxophone for six months, so it's making it's professional debut in Little Shop. What better way is there of doing that than in a show with lots of solos? It's a dream. I love playing it. I feel like Lisa Simpson. It's so cool."

Quinnell was doing pantomime when she was supposed to have her first audition for Pitlochry, and was only offered the season after a recall.

"Up until my first season I'd never been to Scotland, and now I find I've spent three years of my life here and can't keep away. It's a long way from home, but I can honestly say that first year was the best year of my life."

Aside from her work onstage, Quinnell met her actor boyfriend that first season. She's also taken advantage of the scenery. "Just look at the view," she says, motioning towards the bar's windowed facade. "It's not often you get to sit in your dressing room, look out the window and watch salmon jumping. I'm very, very lucky."

Born and raised in Cardiff, Quinnell started performing from an early age with her two sisters and one brother, all born a year apart. Ever since she can remember, the Quinnells have been making music. They learned to play several instruments apiece, and used to sing in four-part harmony for fun, visiting friends' houses and forming ad hoc bands whenever they could.

While this may have been a puzzle for her dad, who'd never seven seen a musical until he met his wife, it was the matriarchal influence from Quinnell's song and dance-loving English teacher mum that fed into her brood.

At school, between helping her mum with her own shows, Quinnell played lead roles in Grease and South Pacific, and started to wonder if she could turn her love of performing into a career. Undecided between acting and music, she opted to study both at Aberystwyth University. She played a young Lady Macbeth, which led to her professional debut, again as Eliza in My Fair Lady.

While she and one of her sisters, who's now head of music in a school in Monmouth, are blessed with perfect pitch, Quinnell is the only member of the clan who's taken things further. While her doctor brother plays in a band for fun, Quinnell's third sister has forsaken music in favour of the fashion world.

In between her first stab at Eliza and Pitlochry, Quinnell understudied the lead in a tour of The Thorn Birds, played "a tarty air stewardess" in Come Fly With Me, a big band musical at Cardiff's Millennium Centre, and has played Snow White in panto. For the future, beyond Pitlochry and a stint as Cinderella, Quinnell has her sights set on other stalwarts of the musical stage. "I'd love to play Sally Bowles in Cabaret," she gushes. "Any part in Chicago, Roxie or Velma, I don't mind. Oh, and Adelaide in Guys and Dolls. I love that part. She's such a character."

Whether she ends up doing these in Pitlochry or the west end, Quinnell retains a sense of wonder at how things have worked out. Especially as sometimes she even gets to keep her clothes on.

"Even now I'll get a pay slip and I think, oh, God, I'm being paid to do something I love. That doesn't happen to a lot of people, so I feel like the luckiest person alive."

Little Shop of Horrors, Communicating Doors and Dear Brutus will run in rep at Pitlochry Festival Theatre until October. Visit www.pitlochry.org.uk.