Jason Aldean performs at Nationals Park. (Kyle Gustafson/For The Washington Post)

It takes personality to sell a country song. But with a complete lack of personality, you just might take that song to No. 1.

Ask Jason Aldean, the Georgia-born everyman who sang a handful of drab chart-toppers during his headlining set at Nationals Park on Friday night. This was a big guy under a big hat singing to a big crowd. But even when he couched his songs in grand gestures — growling electric guitars and flashy pyrotechnics — they never felt more than medium.

When grumblers grumble about today’s country music sounding too slick, too generic, too much like rock music that doesn’t actually rock, Aldean is the guy they’re thinking of. Across five albums — each filled with songs he didn’t write — the 37-year-old has turned his personality gap into his most valuable asset. The less character he puts into his songs, the more room he creates for listeners to relate. His voice isn’t interesting enough to paint a picture. It simply provides a frame.

Of course, all great pop music does something like this, inviting us to transport ourselves into some other state. But Aldean only asks his intended audience to travel short distances, to a mildly romanticized version of rural American life — into a pickup truck, off to the edge of town, out under the moonlight.

That’s the basic story line of “Night Train,” the title track of Aldean’s 2012 album, which, on Friday, felt smoother, flatter and more anonymous than the dirt roads it was commemorating. Anyone could have been up there singing it. Fittingly, it was one of the biggest singalongs of the night.

Tougher to stomach were “1994” and “Dirt Road Anthem,” two hits where Aldean spoke in rhyme, as if out of obligation. Call this rapping if you must, but save your eye-rolls for the hard rock pantomime Aldean presented at the open and close of his set. “Hicktown” and “My Kinda Party” felt souped-up and dumbed-down while the grand finale of “She’s Country” sounded like diet AC/DC and ended with fireworks hissing and popping over the stadium.

Opening act Florida Georgia Line brought its electric guitars to the party, too, but didn’t really need them.

What Aldean lacks in charisma, the vocal duo has almost too much of, thanks to the singing of the band’s livelier half, Tyler Hubbard. On Friday, Hubbard’s voice was tangy, cheesy and a revelation when consumed in moderation — Cool Ranch Doritos for the ears.

Last summer, he and bandmate Brian Kelley were the toast of Nashville with the success of “Cruise,” their mucho-macho courtship anthem that critics swiftly castigated, dubbing the band’s sound as “bro country.”

Those critics were missing out. One summer later, Florida Georgia Line’s juiciest party anthems — “Cruise,” “Round Here” — sounded as irresistible, energetic and overblown as ever. In turn, Hubbard and Kelley spent plenty of their set high-fiving each other. (More bands should high-five each other in concert.)

But the duo also seemed acutely aware that all bros must become men someday. So, they toned things down with their most recent hit, “Dirt,” a pensive ballad about the stuff beneath our feet and the circle of life. “You know you came from it,” they sang. “And someday you’ll return to it.”

It was a simple song about small-town life, but the duo’s harmonies made it feel vast and alive. Turns out, it was co-written by Rodney Clawson, a Nashville songwriter who’s scored some big singles with Aldean.

Could Aldean have turned “Dirt” into a hit, too? Easily. When it comes to personality in country music, it’s all or nothing.