CONCERT PREVIEW

Chicago and REO Speedwagon

7 p.m. Sunday. $36-$76. Chastain Park Amphitheatre, 4469 Stella Drive N.W., Atlanta. 1-800-745-3000, www.ticketmaster.com.

It’s a lite-rock fan’s dream bill, the pairing of Chicago and REO Speedwagon for the first time in their respective histories.

Between them, the bands have sold more than 80 million records and, primarily in the ‘70s and ‘80s, kept the chart trackers busy with a parade of hits, including the number ones “If You Leave Me Now,” “Hard to Say I’m Sorry” and “Look Away” (for Chicago) and “Keep on Loving You” and “Can’t Fight This Feeling” (for REO).

During the tour, which comes to Chastain Park Amphitheatre on Sunday, the two bands will cram as much of their musical histories as possible into separate hourlong sets and then merge for a combo encore that will surely enthrall fans (“Roll With the Changes” and “25 or 6 to 4” have appeared in recent shows).

Chicago is also throwing in the new track, “Now,” from its recently released 23rd studio album, “Chicago XXXVI: Now.”

Before the tour launched earlier this month, REO Speedwagon singer Kevin Cronin and Chicago’s Robert Lamm (vocals) and Lee Loughnane (horns) participated in a conference call with reporters to share some insight into the monthlong joint jaunt.

On the bands sharing the stage for the encore:

Kevin Cronin: "That is probably, for me, the most exciting part of (the show), that we're going to be able to cross-pollinate for a while at the end there. … To me, as a songwriter, there's nothing better than when you take a song and just take it outside the comfort zone, turn it inside out. These (Chicago) guys are like real musicians; we're just a bunch of knuckleheads with guitars."

On compiling their respective set lists, given the extensive catalogs of both bands:

Lee Loughnane: "That is a very good question, 'cause we have an overabundance of songs. Even when we play shows on our own, we play a two-hour show and can't get all of the songs that have become hits into the show."

Cronin: "We have a core bunch of songs that if we don't play them, there'll be an angry mob waiting for us outside right around the tour bus. There are those songs that people buy tickets to come and hear.

“I’ve always adhered to the theory that people are spending their hard-earned money to come and see us play, so we’re going to give them the songs that they want. To me, there’s nothing worse than going to a concert to see a band, and they leave out some of their bigger songs for some reason. I’ve never understood why people do that. It makes me mad when I go to a show and that happens.”

On preparing vocally for tours:

Robert Lamm: "On show days I don't talk, and I'm not a really talkative guy anyway, so I guess I have a leg up on actual concert days. … Once in a while, there is a rehearsal or something before the show. I find that if I sing at the rehearsal, I'm already warmed up by the time the show hits. Warming up is the key."

Cronin: "I agree. It really is about disciplining yourself. If the drummer has a cold, the concert goes on. If the singer has a cold, it's a little bit of a different situation. Robert and I walk around with our instrument 24 hours a day. When you think about it, there are these two little hunks of meat in our throats (and) basically the whole organization rests upon it.

“It’s definitely a little bit of a pressure to be a lead singer, and so you’ve got to respect that, and you’ve got to try to get a good night’s sleep.”

On touring after more than four decades:

Cronin: "We're staying in nicer hotels now than we did in the '70s, for sure. Probably the best thing that's changed is tour buses have satellite TV now. If there's a sporting event that you want to catch, you can DVR it on the bus, then as you're driving to the next town, you can watch that Blackhawks game or that Lakers game, or whatever it is.

“It makes the travel a little bit easier. The buses are beautiful, they run smooth, they’re quiet, the air conditioning’s better. It’s better than the 1972 Chevrolet Impala station wagon that we traveled in back in the ’70s, for sure.”

Loughnane: "Yes, we do complain about traveling sometimes, but the most important thing is the show. Both bands love playing for people, and we do a good job at it, and we look forward to doing it again and beyond."