Classic-rock legends The Doobie Brothers couldn’t have foreseen all the highs and lows when they formed four decades ago. The California-born group is responsible for some of the biggest hits of the ’70s, including “What a Fool Believes,” “Black Water,” “China Grove” and “Listen to the Music,” all while undergoing dramatic stylistic shifts and persistent personnel changes.

Michael McDonald took the reins in the mid-’70s, before the act temporarily disbanded the following decade.

The subsequent reunion and years since have brought back a handful of albums, successful tours and some heartbreak, like March 12’s passing of drummer Michael Hossack.

Still, The Doobie Brothers keep a level head.

“Nobody expected anything at anytime. We were taking it a day at a time. Still do,” guitarist and founding member Tom Johnston said. “We’ve been very fortunate all the way around.”

In some ways, the band feels like nothing has changed at all.

“We had a plane back in the ’70s — that’s about the only big difference,” Johnston said. “We keep as busy as we ever were. Every year, we are out, doing anywhere from 80 to 90 shows.”

According to him, the group has yet to phone it in, despite that longevity.

“The live show sounds better than ever,” Johnston said. “Everyone makes a point to be at the top of their game.”

The band’s latest album, 2010’s World Gone Crazy, was its first in a full decade. Even now, a year and a half removed from its release, Johnston and company are still buzzing with excitement and enthusiasm for the disc.

“This is the best album we’ve done since Stampede,” he said, comparing World to that 1975 smash. “Everyone walked out of the studio thinking, ‘Yeah, we did a great job.”

Currently, no plans for a follow-up exist, but Johnston doesn’t deny the possibility. For now, however, the bulk of the band’s energy is fixated on touring, with a co-headlining tour with Chicago coming up this summer.

“Playing live is always the best part for me, and always has been,” Johnston said. “Every show is different, even playing the same songs. The room is different, the crowd is different, so it’s always a challenge to get out there and get the people rocking.”