But at the Fillmore, which holds about 3,600 souls on the best nights, it's deflating to see the place barely one-fifth full.
Keen is best known for stirring up an instant party atmosphere - frat boys howling "Robert Earl Keen! Robert Earl Keen!" certainly help kick off the fiesta - and he needed to pull out the stops this evening. As he took the stage, this hottest of concert nights felt more like a Tuesday evening gathering with no keg.
The man from Bandera, Texas came out firing. Keen opened with fan favorites typically reserved for later in the set - first, a blistering reading of James McMurtry's "Levelland," which lead into his own buoyant "Corpus Christi Bay" and then Terry Allen's rollicking "Amarillo Highway."
He stacked the opening wisely. That raucous trio rapidly transformed the Fillmore into a rowdy Texas dance hall. It stayed that way for the next two hours.
Thank Keen's band - including longtime cohorts Rich Brotherton (guitar, vocals) and Bill Whitbeck (bass, vocals) - for that. The crack outfit burst so quickly from "Amarillo Highway" into "Gringo Honeymoon's" "Think It Over" that the audience seemed unfazed that sound problems caused Keen to butcher a full verse in the former.
One downside to Keen's live shows is that not much changes from year to year. Sure, he mixes around the set list nightly, but it can be like hearing the same greatest hits package over again. To that end, only three songs from his newest album, "What I Really Mean," made it into the mix ("For Love," "Mr. Wolf and Mamabear" and the title track).
It's a shame, because "What I Really Mean" might be his best effort since 1994's "Gringo Honeymoon." Both are filled with Keen's trademark dry wit, but dig the deepest for emotional truths.
In fact, for those who prefer Keen's more introspective singer-songwriter side, it can be frustrating to come to terms with the fact that his following largely has been gained through toss-off novelty tracks like "Five Pound Bass" and "Merry Xmas to the Family." As usual, those earned some of the loudest hoots tonight.
Keen did his best to cater to his more deep-browed fans, though, sprinkling fine story songs like "Old Mexico," "Feelin' Good Again" and his stellar cover of Steve Earle's "Tom Ames' Prayer" throughout the set. His best combination of the celebratory and cerebral, of course, is "The Road Goes on Forever," and tonight he closed out the main set - as is his custom - with it.
The band returned for a one-song encore with "Farm Fresh Onions," though the quickly dispersing crowd seemed content to go out with his biggest hit.