When Delirious first played the Ichthus Festival in 2001, then- festival director Rick LaDue put the booking in historical terms.

"We're the oldest Christian music festival in the country," LaDue said. "Delirious is a band that is part of Christian music history. We needed to meet."

The history that Delirious made was integrating praise-and-worship music with rock 'n' roll.

Until the late 1990s, there was Christian pop and rock that you heard on the radio, and contemporary praise-and-worship music that some churches used in their services. But it was not often — maybe the occasional chorus, like Amy Grant and Michael W. Smith's Thy Word — that you heard a Christian top 40 song used in worship services.

Then, Delirious started playing youth events in England, pumping up the praise with songs like Did You Feel the Mountains Tremble.

Now, just eight years later, Delirious returns to Ichthus for its last festival appearance in Kentucky, at 10:20 p.m. Saturday.

Later this year, on Nov. 29, the band will play a farewell concert in London, then the members will go their separate ways.

"We're happy at what God's done over the years but sad because it's going to end," frontman Martin Smith said in a phone interview. "It's a good time to do that. It's not a breakup in that we've fallen out or anything. We're still fantastic mates, and in the future we may play again. But for now, it's time to pursue other things."

All of the band members are fathers now, which makes them want to be closer to home, and they have other music and ministry projects to pursue.

Keyboardist Tim Jupp, for instance, has launched a music festival in England, and Smith is heading up CompassionArt, a new charity to combat international poverty.

Delirious recently built a medical center in India, illustrating the biggest turn in the band's career, changing a focus from pure worship music to encouraging its audience to take up social-justice causes with songs like Our God Reigns and its last studio album, Kingdom of Comfort.

"We're called to look outside our own lives and see that the majority of people living on the planet are miles and miles away from the affluence of basic wage-earners in the West," Smith says. "We are passionate about inviting people to see places like India and Africa and highlighting those things. It has been a great journey for us, and a lot of the songs recently have been reflecting that journey."

The songs are, of course, what will endure with Delirious. A number of them are contemporary worship staples. That frequently puts members of Delirious in the position of going to a service and, whether people know they are there or not, hearing their own music.

"It happens quite a bit where you find yourself somewhere and they're doing one of your songs, and you're always amazed to hear all the different versions that happen," Smith says. "We're humbled first by the fact that people like the music, but even more that they want to do it themselves and do their own version."

He's heard things like a "jazz-lounge version of I Could Sing Your Love Forever that was brilliant."

Asked about his own favorite songs, Smith doesn't go for the standard "all my songs are like children" answer that many artists give. He very quickly names the hit History Maker.

"That's been a constant of our career, to tell people, 'You must believe you are on the planet to do more than just exist,'" Smith says. "You've got to go for your dreams and what you feel to be inside of you — to be a part of making history together."

That provokes the question: Does Smith think, as others do, that Delirious has made history?

"Other people should be the judge of that," Smith says. "The great thing about Delirious is we've been around for a while, 17 years this year, and that's a good, long stint for a rock band. We're amazed some of these songs have become part of the woodwork and people are singing our songs across the planet. That's just amazing."