Al Harlow knows when you're part of a legacy band like Prism, you don't tinker too much with the classics.

That's why they still open most of their shows with Spaceship Superstar and close with Armageddon, the two biggest hits of their 30-year career.

But he also knows you have to keep moving forward. So when they play the SuperEx on Saturday night, they'll find room for some songs from Big Black Sky, which was released last year and is their first studio album in 11 years.

"Some fans would have been happy if I'd rewrote Spaceship Superstar backward and swallowed some helium and tried to imitate the way we used to be, but I couldn't do that," says Harlow, the singer responsible for hitting the high notes.

"With Big Black Sky, I was kicking things forward and it was embraced very well, but I realize, 'how would I feel if I go out and bought an album of an old favourite artist of mine?' I'd want it to tweak some warm comfort zone that relates to my past with that artist."

Harlow is the only original member from the Vancouver band that was formed in the late 1970s. Two members -- producer Bruce Fairbairn and lead singer Ron Tabak -- have died. Drummer Jim Vallance hasn't toured in many years, but was in Ottawa last week playing piano for his long-time pal Bryan Adams.

Harlow now handles the singing for Prism.

"I used to be the high harmony guy, wrote a number of the songs and stood beside Ron Tabak back in the day and we sang together," Harlow says. "I used to sing all the choruses, now I'm singing all the verses too."

With Big Black Sky, Harlow says he wanted to take the listener on a journey, contrary to the "iTunes world where you can just cherry-pick the songs and load up the iPod."

"It should start at Point A and take you to Point B," he says. "It's spiritual but it doesn't preach. I like lyrics that leave plenty of room for subjective interpretation."

But he couldn't stray too far from Prism's roots.

"We have to be wise enough to know which side our bread is buttered. We wouldn't want to do a Spinal Tap, 'hope you like our new direction, here's a 17-minute jazz suite.' Because I know what it's like to be on the other end.

"It's hard to be objective when you're at the centre of it. For you and me and everyone, we can date events of our lives by the songs of the time. Everyone has their graduation song or their crazy teenage years song so when people come to me and say, 'Night to Remember reminds me of grad night or some other night,' well all it reminds me of is being in the studio and trying to get the tambourine part right, so I don't have that attachment, but I understand the music is still alive and has stood up, and that's a good feeling."