Though their history began and ran concurrently with some of the modern era’s greatest and most beloved alternative bands (Yo La Tengo, R.E.M., My Bloody Valentine), Antietam never garnered anything close to the attention or accolades of those acts. From 1985 to 1994, the Louisville band recorded for such respected labels as Rough Trade and Homestead, but had a difficult time making a mark beyond the considerable respect of their peers, particularly for guitarist and frontwoman Tara Key’s inventive playing. The two-disc Opus Mixtum is perhaps a little overwhelming to serve as an introduction to the band, though its contents clearly demonstrate that Antietam’s relative obscurity compared to their peers is a shame.  So if you’re like me, and the release of Opus Mixtum is the crest of a wave of new knowledge, you might wipe out a few times (at over an hour and a half, it’s a damn big wave), but you’ll want to keep trying.

It’s not just the size of this collection that daunts, but the variety. The band boasts a wide range of influences from all over the musical spectrum and shapes them into distinct, uncompromising combinations. Opus Mixtum’s opening salvo of “Tambo Hope”, “RPM” and “Shipshape” establishes the project’s everything-all-at-once approach.  The instrumental first track is a slight bit of tambourine, finger-picked guitar and what sounds like a synthesized cello. Though barely over a minute in length, it’s steady and repetitive—hallmarks of Antietam’s sound— and a brief warm-up to a long listening experience.  “RPM”, as its name implies, is revved up and urgent.  It’s also highly melodic, and again, repetitive. Key often fixates on a melodic line, and rather than extrapolate from it, twist or embellish it, pummels it into the ground.  But what keeps the somersaulting “RPM” or the choppy “Shipshape” engaging is the straightforwardness of the structures pitted up against the blurred squall of the guitars, muffled deadpan vocals, and stylistic versatility.

For such a long and varied work, there is a conscious lack of bullshit.  “Steel G” gets mileage of one bent steel string (err, the G perhaps?) punctuating a summery arrangement of organ and strummed acoustics.  “Arrowhead Syrup” is a bit more baroque, sounding something akin to Lambchop’s recent instrumental work while maintaining a punkier edge. “Needle and the Eye” is full-on Loveless style bluster and haze. “You/I” is a buzzsaw, a perfectly concise garage-punk howler, built around the angular interplay of chunking guitar and drums.  Key sounds tough and confident in the murk, with only a few syllables about attraction and desire (I think) escaping. The band attacks every song with a mature intensity, and if there’s any weakness, it’s that the relentless and weight of Opus tends to leave one feeling crushed after a while. 

Originally intended as two separate discs, one for the straight-up rock cuts and one for the atmospheric instrumentals, the band instead chose to weld the two together into a sprawling behemoth.  Perhaps if Opus Mixtum were divided as such, it would be less befuddling and disorienting. But the jumps from bruisers like “You/I” to the more exploratory material like the epic closer “Tierra del Fuego” call more attention to the nuances in each, and leave the impression that although Antietam may never be as well-known as its peers, Key and company are just as capable, dynamic and deserving.

• Multiple songs MySpace