CHEYENNE (AP) - Cheyenne Frontier Days has found a handful of groups for this summer's opening night act following the recent pullout of pop rockers Matchbox Twenty.

Frontier Days bills itself as the world's largest outdoor rodeo, held over 10 days each July. The Guess Who, a Canadian rock band, will headline the July 18 show. They will be joined by the groups WAR, Atlantic Rhythm Section and Firefall.

According to a news release, The Guess Who started in 1962 and has achieved 14 top-40 hits, including "American Woman" and "No Sugar Tonight." WAR rose to fame with 1970s hits including "Why Can't We Be Friends," and "Slippin' Into Darkness."

Firefall, based in Boulder, Colo., toured the world from 1976 to the early 1980s and sold millions of albums and has three gold records, according to the release. Its hits include "You are the Woman." Atlantic Rhythm Section blends country, blues, soul and rock and has been playing for more than 30 years.

Matchbox Twenty canceled plans to perform at Frontier Days earlier this month, and lead singer Rob Thomas posted an announcement on the band's Web site blaming the cancellation on the rodeo's alleged mistreatment of animals.

Frontier Days Contract Acts Committee Chairman Joe Lopez said he's happy with the new lineup of opening-night performances.

"We always have a backup plan on any night show," Lopez said. He said it wasn't difficult for the committee to put the show together.

Ticket prices for the show are considerably lower than they were for Matchbox Twenty, which were $38-$68. Tickets for this show will run between $18 and $33 and will go on sale on Thursday.

With the recent negative attention Frontier Days has received, Lopez said he wanted to bring some positive energy to the event. Along with lower prices, the show also will begin two hours earlier than normal, at 6 p.m. instead of 8 p.m. The concert will end at about 10:30 p.m.

Lopez said he hopes the earlier time will allow more families to attend the concert. He said he expects the concert will attract people from their teens and 20s to people in their 50s.

"We turn negatives into positives, and that's what we're looking at doing," Lopez said.