Opportunity Knocks, but . . .

One thing clearly was missing from Willie Nelson and Leon Russell’s show at the Coach House Monday: spirit.

“Spirit” is Nelson’s first studio album in five years and one of his most satisfying in the last 15. It was released last spring, so this was the first time since it came out that Nelson has played locally. Yet he played just one song from it, the haunting “She Is Gone.”

It was a shame on several fronts. “Spirit” isn’t a concept album the same way that Nelson’s “Phases and Stages” and “Red-Headed Stranger” are. But it deserves a place alongside those two for the quality of the songwriting, the skill of Nelson’s singing and the way one song links to another, making for a cohesive work that touches on the loss of love, acceptance of the loss and the realization that life goes on.

The album is built on spare arrangements, often just Nelson’s plain-speaking acoustic guitar and his sister Bobbie’s unadorned piano work--which would seem to have made it ideal fodder for the duo format of the concert (the first of four scheduled for Monday and Tuesday, and the third engagement of Russell and Nelson at the club in less than a year).

Yet the opportunity went untapped. As they did last December and again in February, Nelson and Russell (aided by Nelson’s longtime harmonica-playing sidekick, Mickey Raphael) stuck almost exclusively to their most familiar songs (to the delight, it must be noted, of the sold-out house).

For Nelson, any setting that allows him to break free of his straitjacket Family Band concerts has its rewards, the first of which Monday was his loose, jaunty take on “My Bucket’s Got a Hole in It,” with Russell reeling off propulsive gospel piano underpinning for Nelson’s carefree vocal.

Russell’s gospel roots also came out, via his pumping left hand, during “On the Road Again,” a warhorse from the Nelson canon that had little right to sound as energetic as it did.

But those were exceptions on a night when another kind of spirit--musical spirit-- often was missing in action.

Russell shifted meter oddly throughout his performance of “A Song for You,” bleeding it of any momentum, and it wasn’t the only time that problem cropped up during the 70-minute set. Part of the blame goes to a sound mix that elevated Russell’s piano over everything else, forcing Nelson’s guitar--and, even more so, Raphael’s harmonica--to fight to be heard.

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But it wasn’t only a technical issue. Both Nelson and Russell often reduced songs to a series of bleeding rhythmic chunks--Nelson by spinning out guitar fills that halted as quickly as they began, Russell by metronomic chord pounding that robbed phrases of fluidity.

It was most glaring when Nelson sang Hoagy Carmichael’s “Stardust”--one of the most elegantly sculpted melodies in American popular music--as a string of starts and stops instead of one long beautifully elastic line.

Russell, whose playing is grounded in boogie-woogie, Fats Waller stride and New Orleans tradition, offered only glimpses of command of those styles. And, as during both the previous duo engagements here, Russell, the erstwhile “Master of Space and Time,” incorporated intrusive synthesized string sounds far too frequently. As the chaos theorist in “Jurassic Park” noted so aptly just before all hell broke loose, the issue of whether technical feats can be accomplished never should take precedence over whether they should be.

The collaboration gave no hint that it has becoming overrehearsed--the interplay was so casual that at times it felt disjointed, as if the musicians were running through some numbers for the first time. Liberating spontaneity can flower under such circumstances, but Monday it more often caught the men searching for elusive common ground.

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The Paula Nelson Band, which opened with an impressively confident set, is led by one of Willie’s daughters and includes another, Amy, who harmonized sweetly with her gutsy-sounding sister. Again, though, the sound mix overemphasized the keyboards, rendering the lyrics indecipherable (of the seven songs in the set, five were Paula’s originals).

But there was no missing the unforced power of Paula’s singing, which ran from the nasal bluesiness of Janis Joplin to a sweetly quavering warble a la Victoria Williams. The sisters got tight backing from their recently assembled four-man band, most notably from the driving second-line foundation laid down by drummer Stuart Nesbitt for a seductive version of Ray Charles’ “If You Were Mine.”

Any specter of nepotism quickly vanished under the Nelson girls’ strong performance.