TWO-AND-A-HALF years ago, Newcastle band silverchair vanished from the musical radar. After sales of six million albums worldwide and more top 20 hits than any other Australian artist in the past five years, the strain to sustain such success since the age of 14 had taken its toll. Daniel Johns, Chris Joannou and Ben Gillies needed to rest.

The three mates returned to the music world this year, for the Big Day Out, their time away allowing them to refresh, capitalise their name and take their sound in a new direction.

Their fourth album, Diorama, will be released in stores on Monday, featuring more uplifting, moodier music, far from the darker sound which sent their debut album Frogstomp to the top of the charts.

"Between every record has been some crazy step," says Joannou. "Whether it be a new direction, every step has been quite different from the last. (With this step) we've all become our own people. I suppose when you're growing up, you're all pretty young guys full of testosterone, with all similar likes and tastes and what not. Now we've settled in our own style of things we like. We're still good mates . . . but the best thing is that we have got our own personal private lives outside of the band. As time went on after a couple of records, that's when things started to get a bit tiring. With the time off, it's helped us become happier with life again and that all just comes through the music.

"He (Johns) is just happier within himself and he's painting with colours now. Not just shades of grey or black."

Painting with colors is an analogy for embracing more melody, brighter lyrics and exploring more diversity with more instruments, Joannou explains. Co-produced by Johns, the new album was recorded in Australia and mixed in Los Angeles by producer David Bottrill (Tool, Peter Gabriel). Legendary Beach Boys and U2 collaborator, Van Dyke Parks, contributed orchestral arrangements to three tracks, with Paul Mac and Jim Moginie helping out again after work on the group's last album Neon Ballroom.

Already described by Rolling Stone magazine as "one of the boldest musical statements ever made by an Australian rock band", "Diorama" means "a world within a world" - an experience the band wants to achieve. "The orchestra stuff was a lot more in depth," says Joannou. "There were bass flutes, harpsichord, different percussion stuff.

"I don't know if you'd call it a gamble or a risk or anything, but one of the things you've got to almost expect if you change or the band evolves is whether the people will evolve or change with the band or not. We just want to get out there and perform." But they may have to wait a little longer than expected to perform again - perhaps indefinitely.

Two weeks ago, Johns was diagnosed with a crippling virus - likened to arthritis - which has caused his knees to swell, making him unable to stand. The group was forced to pull out of Hobart's Down South Festival, the first gig they've postponed.

"To tell you the truth, they don't know how long it's going to go for or whether it's going to stop," says Joannou. "He's in a bit of pain and he's trying to get over it. He kind of comes up and down." What if this was permanent and Daniel couldn't perform? "We'd still keep making music as a band," says Joannou, "but maybe we'd have to do an Internet gig once a week in his lounge or in his recliner. Either that or get him an A-frame to go on stage."