Celebrating 30 years of playing together, Russell Hitchcock and Graham Russell are the only two original members of Air Supply left - but they are the heart and soul of the group.

As long as they're together feeling the love, that's the way it'll stay. They'll be bringing every one of their love-laden songs along to the Winspear Centre tomorrow night.

Chatting from his hotel room in Montreal, 57-year-old Hitchcock tells the story of his unlikely meeting with Russell back in Australia - in a production of Jesus Christ Superstar.

Hitchcock wasn't a singer. It was his girlfriend who convinced him to go to the audition.

"I felt like a defective car. I got recalled like three times. The last time they said, 'We'll offer you a part in the show.' And that's where I met Graham. But I hadn't sung anything until I was 25."

From there, Russell and Hitchcock assembled a band and lucked out a couple of years later with an opening slot on Rod Stewart's North American tour, something their record company didn't like.

"They said, 'You shouldn't leave because your career is not established and we can make you the biggest band in Australia.' And we both hadn't verbalized it, but Graham and I both said basically at the same time, 'We don't want to be the biggest band in Australia, we want to be the biggest band in the world.' "

Shortly after that tour, Air Supply decided to make a Best Of album from their first two Australian releases. They returned to the States to do it.

"We used American session musicians instead of the band, so that kind of fractured things a bit and then the third guy left," says Hitchcock of Air Supply's original lineup and third front man Jeremy Paul. "We just decided then, that, for every reason, it's the two of us. You can weather changes in personnel, you know, band guys coming and going, without affecting the public's perception of who you are."

Touring behind The Singer and The Song, an acoustic collection of hits from the '70s featuring Hitchcock "the Singer" and Russell "the Song" on their own, Air Supply will appear as a full band tonight.

"Once people see the band and it's not two guys and two acoustic guitars sitting on stools going la, la, la, it's a powerful rock 'n' roll show, we typically get invited back," says Hitchcock.

Although he may consider their sound a little heavier than objective opinion would, their dominant subject of love is an essential part of Air Supply.

"There's no premeditated intention to write about it. It's just what (Graham) does and we don't question it. We don't have to defend it, it's just what Air Supply is synonymous with," says Hitchcock of his songwriting partner, adding it's a talent he doesn't share. "I don't write songs. I can't. I mean I've tried to write lyrics and I look at them and they all suck, so I throw them away."

Not only has their subject matter identified the group on a global scale, but it's helped open doors in strict countries, something the band began doing in its infancy.

"In 1980 we got invited to play Seoul in (South) Korea and we'd only done limited touring in North America, so we jumped at that chance. We went over there and the amount of fans that we had was quite staggering," says Hitchcock. "We were the first band to play Hanoi in North Vietnam. We were the first band to actually do more than one date in mainland China. We played Cuba last year. We've been really lucky to be able to go to these places."

Russell and Hitchcock have toured as Air Supply every year since 1975 and have no intention of slowing down. Having already been to India this year, Hitchcock says they're booked until next August with dates that will take them through Central America, China, Taiwan, Korea and then back to Australia.

By that time, Air Supply plans to release Zed, their first album of original work since 2003's Across The Concrete Sky.