Some band’s musical identities are entirely bound up in a single, sometimes peripheral, instrument, sound or refrain. This is, in parlance, the gimmick. The gimmick defines the band, makes it unique, is its lifeblood—without the gimmick, the band cannot musically subsist in any recognizable form. Familiar gimmicks include (or, better, should include) Jethro Tull’s flute, Jimi Hendrix’s Arbiter Fuzz Face, The Police’s delay pedal and Peter Frampton’s Talkbox—all part and parcel with their performers’ legacy.

In the same way, the subtle twang of the banjo is linked inextricably to the idea of Wilco. To be sure, the banjo isn’t featured on all of Wilco’s tracks, but it remains their most distinctive feature, and the cornerstone of their unique no-depression, “alt-country” timbre. And when multi-instrumentalist/technician Jay Bennet (i.e. the banjo guy) left Wilco earlier this year, so too did the all-defining Wilco gimmick. Bennet left behind a deflated effigy of a band, an artifact which in its present incarnation is almost unrecognizable (save Jeff Tweedy’s unmistakably textured vocals). In a sense, the whole quiditas of Wilco, at least the Wilco of 1996’s epic double album Being There, was lost with Jay Bennet.

But perhaps this is too harsh or uncharitable an assessment; perhaps it doesn’t allow for an evolving sound or an evolving musical vision; perhaps it isn’t fair to expect a band to cling unflinchingly to the musical mores of their formative career. Indeed, these are important considerations, but change at what cost? In the estimation of many devoted fans, Bennet’s departure comes as a dear loss to Wilco’s nuanced sound and is a change for the worse.

It is this sentiment, above all others, that seemed to characterize fans’ responses to Wilco’s most recent Boston show, on Oct. 2 at the Avalon. A Diesel-clad, late-20-something crowd (college radio, six years ago) was, on the whole, more interested in cheap beer and idle conversation than they were in the newly [mis]conceived band. Lukewarm applause and half-hearted song requests abounded for the duration of a painfully short set.

Adding insult to injury, sound levels were badly regulated—Hammond organ, an essential Wilco ingredient, was almost inaudible; the bass guitar was muddled and overpowering, and, more generally, instrumental separation was poor. Bennet’s replacement, Leroy Bach, seemed overly conservative in his supplemental instrumentation and Tweedy lacked his characteristic attack on the guitar. All of these things notwithstanding, renderings of “A Shot in the Arm” and “She’s a Jar” were surprisingly good (though, again, organ layers were uncharacteristically weak) and new drummer Glen Kotche filled Ken Coomer’s proverbial shoes rather admirably.

But any lingering ill sentiments in the audience were quickly allayed when guitarist/producer Jay O’Rourke joined Tweedy and the band for three or four encore tunes. O’Rourke, a veritable living hero among indie rockers, offered pleasantly surprised fans a few incisive, gritty guitar solos and seemed to awaken a dormant life force among the Wilco band members. O’Rourke’s unique interpretation was particularly propitious because it suggested that, with a few minor—but crucial—adjustments, Tweedy might define for himself an entirely new and marvelous musical telos.

After all, considering the losses counted by Tweedy in the past year, including a break with long-time distributor Reprise Records, and the departure of two indispensable band members, he’s managed to salvage what might (if the songs played with O’Rourke are any indication) still develop into something wonderful, if wholly unlike previous musical ventures. Due in large part to these recent hardships, Wilco’s forthcoming album, Yankee Hotel Foxtrot, has been indeterminately postponed. For the time being, fans can (legally!) download the album off of Wilco’s official website, www.wilcoworld.net.

There is, then, still a modicum of hope for Wilco, and at the very least it’s clear that Tweedy is still committed to the quality of his fans’ listening experience by offering good faith efforts to make an unfortunate situation more negotiable. Tweedy needs time to convalesce, collect his musical thoughts and regroup, and we should be willing to grant him at least that much before passing judgment. Until that time, though, a $25 ticket investment will likely return few dividends.