Dan Auerbach and Patrick Carney brought their ’A’ game to Boston on the last day of July, where the duo passionately offered up gratifying chunks of their early material. Unfortunately, they also brought two other musicians with them and the duo periodically expanded to an uninspired quartet for takes on newer Keys material that proved largely unsatisfying.

They began the show by bombarding the sold-out crowd with a selection of heavy blues tunes from their first three albums. ’Hold Me in Your Arms’ and ’10 AM Automatic’ were great and ripped from the stage with a fuller, grittier, and more powerful sound than was captured in the studio. Dan’s Telecaster licks – thick, swampy, and supremely catchy – were fantastic and Carney‘s resourceful, intuitive work on the low end allowed his band mate to confidently channel his inner blues-man without stepping on any toes. ‘Stack Shot Billy’ was another highlight from early in the set. After a brief but alluring Eastern-tinged guitar intro, the song ebbed and flowed, occasionally culminating in a sonic battle between Auerbach’s soaring slide riffs and Pat’s rhythmic cymbal/bass-drum combo – the winner? The audience.

A third of the way through the set, Nick (bass) and Lee (keyboards) came on stage for ‘Same Old Thing‘, but much like during ‘Ten Cent Pistol’ later in the evening, their contributions were largely superfluous. Dan Auerbach told Rolling Stone that he and Pat had “…tried playing with other people, but it was never as easy as playing with each other.” These difficulties adjusting to the new format were on full display as the four-piece played numerous selections from the Keys’ impressive new album Brothers, many of which sounded either mechanical and plodding (‘She’s Long Gone’) or cluttered and garbled (‘Next Girl’). And sadly, many of the tunes that stood to benefit most from the additional musicians weren‘t even fully fleshed out (‘Everlasting Light’ lacked backing vocals and the uber-funky dub bass line in ‘Sinister Kid’ was abandoned entirely).

Not that they didn’t have their moments as a foursome. Everyone hit their marks during the Gary Glitter-esque romp ‘Howlin’ for You’, and ‘Tighten Up’ was also in fine form, perhaps as a result of all the additional run-throughs its received recently on late night TV. During ’Chop and Change’ – a fantastic new song that gulp appears on the Twilight Eclipse Soundtrack – Auerbach’s gravely voice and gentle maraca shakes were complemented nicely by Lee’s haunting keyboard lead, combining to produce a juicy slice of blues saturated 60’s psychedelia.

But there’s no question that the best music of the evening came when it was just Dan and Pat onstage, and as the duo drove that point home late in the set with a soulful take on ‘Your Touch’ and a swingin’ version of ‘I’ll Be Your Man’, I wondered why they ever felt the need to stray from such an amazing two-piece collaboration in the first place.