When Nine Inch Nails [ tickets ] anchorman Trent Reznor announced last fall that NIN no longer was chained to a record-label contract, and promised "a direct relationship with the audience," even the most optimistic of fans couldn't have imagined that the first salvo from the emancipated NIN would come so soon or be as substantial as "Ghosts I-IV."

Exercising his newfound freedom, Reznor surprised fans on a recent Sunday night by dropping "Ghosts," an instrumental set originally conceived as an EP that instead swelled to a gargantuan three-dozen tracks clocking in at nearly two hours. (The set is available in a number of different digital and physical formats via NIN's website.)

After dabbling in instrumentals over the course of his career--a track or two here and there, spread across various releases--Reznor gives his vocal chords a rest, and to great effect. Because his sonic palette encompasses just about every sound imaginable, an instrumental album from Reznor is truly an auditory adventure.

The songs on "Ghosts I-IV" run the gamut from lush piano numbers (which, as fans of NIN's 2002 EP "Still" can attest, are some of the most moving pieces in the arsenal of an act known more for its full-on industrial fare) to blipping-and-bleeping electronica, to all-out buzzsaw-like assaults on the eardrums. Surprisingly, out of 36 songs, there are, at most, maybe two cuts that veer too far into the realm of jarring noise. If the trade-off for those two numbers is a batch of 34 stellar tracks that evoke all manner of emotion (if anything, "Ghosts I-IV" is a soundtrack for your imagination), consider it a bargain.

Couple the absence of vocals and paucity of hooks with the sheer volume of material, and you have a collection that requires the investment of repeated listenings in order to get that "Oh yeah, I like this one!" effect when a given song kicks in. Those willing to make that investment will reap some serious musical dividends.