The Eagles are a business. A big business.

That’s obvious if you watch “History of the Eagles,” a three-hour, warts-and-all 2013 documentary about the bestselling American band of all time.

That’s obvious by the absence on the current tour of longtime guitarist Don Felder, who’s suing Eagles leaders Glenn Frey and Don Henley.

That was obvious by the Eagles’ hand-chosen opening act Wednesday at sold-out Target Center — JD & the Straight Shot, fronted by Jim Dolan, chairman of Madison Square Garden, owner of the New York Knicks and Rangers, and $125 million partner with Eagles manager Irving Azoff in a brand new entertainment management company.

At Target Center, the famously fractured Eagles were predictably businesslike — professional but not passionate, efficient but not energetic and seamless but not spontaneous. The show is billed as the History of the Eagles Tour but Frey seemed determined to turn Wednesday’s three-hour performance into a lecture demonstration at the College of Eagles Knowledge.

Early on, he promised that the group would educate as well as entertain. That meant clips from the film about what book inspired this song and how they told that producer it’s time to rock. It also meant a lecture about the night’s harvest moon and playful scolding when Professor Frey mistakenly said CD instead of tape and the fans laughed. “I’ll tell you when to laugh. That wasn’t a joke,” he half-joked.

The show, which loosely followed the Eagles history, started startlingly low-key in a coffeehouse mode with Frey and Henley duetting on “Saturday Night” on acoustic guitars. Then Bernie Leadon, the Minneapolis-born guitarist who was a member from 1971 until 1975 and has been invited back for this tour, joined for “Train Leaves Here This Morning.”

But this was a slow train coming, this opening 67-minute set. To be sure, Henley was in terrific voice, soaring better than ever (his has aged more impressively than Frey’s), and the harmonies were spot-on, though it took eight singers to produce them. In the longer, post-intermission set, the profs skipped the history lessons and concentrated on the music, which sounded true to those recordings that were the soundtrack of 1970s for white middle-class America.

If the Eagles behaved like rock stars offstage in their heyday, they never learned how to act like rock stars onstage. The unanimated Henley and Frey, both with grimacing faces, couldn’t work up a sweat Wednesday even though the air conditioning was underperforming.

But Joe Walsh gave the Eagles — and the 16,000 members of the Sitting Majority — a swift kick with his guitar heroics, playful antics and spirited vocals on such non-Eagles tunes as “Funk #49,” “Rocky Mountain Way” and “Life’s Been Good.” Every lecture hall — even an arena-sized one — needs a class clown. Henley and Frey should give Walsh a big raise — he’s the Eagles’ most bankable in-concert asset.