By late 1981, the Grateful Dead were a band that had quietly settled into one of their most underappreciated grooves. Brent Mydland, now two-plus years into his tenure as keyboardist, had shed the tentativeness of his early nights and was playing with genuine authority and fire. Jerry Garcia's voice and guitar were in solid form, and the band was deep into the arena circuit — the big rooms that defined their early-eighties existence. This was not the cosmic wilderness of 1972 or the exploratory peaks of 1977, but a working band hitting its marks with surprising frequency, and December of '81 found them on the road in that pre-holiday stretch when the Dead reliably delivered for Midwest crowds hungry for a night outside the ordinary. The Rosemont Horizon, just outside Chicago near O'Hare Airport, was a classic mid-sized arena of the era — not glamorous, but acoustically workable and large enough to hold the faithful in real numbers. Chicago and its suburbs were always strong Dead territory, and the Horizon saw the band multiple times through the eighties. There's something about the Midwest crowds — attentive, a little less scenester-y than the coasts — that often coaxed focused performances out of the band, and this date is worth investigating on those grounds alone.
What we have confirmed from this show is Estimated Prophet, and that's not nothing. "Estimated" is one of the great vehicles in the Dead's second-set arsenal — that lurching, reggae-tinged 7/4 groove that Garcia and Weir lock into with such strange precision, building tension through repetition before the song opens up into whatever the band decides to do with it. By 1981 it was a well-worn classic, but Brent's organ voicings gave it a different texture than the Keith Godchaux years, and the notation in the database of "Estimated Prophet >" suggests this one didn't just resolve cleanly — it went somewhere, likely dissolving into a second-set excursion that's worth following wherever it leads. That transition moment, when the groove begins to loosen and the band starts reaching, is exactly the kind of thing that separates a serviceable performance from a memorable one. The recording circumstances for this show aren't definitively known, but Chicago-area tapes from this period vary from decent audience to genuine soundboard quality — worth checking the lineage notes before you sit down with headphones. Either way, if the "Estimated >" delivers on its promise, this is an evening worth your time.