Whether or not you’re a fan of his music, it’s hard to argue that Trent Reznor, the creative mastermind of Nine Inch Nails, is constantly at the forefront of innovation. For his last album, Year Zero, Reznor teamed up with 42 Entertainment to develop a massive viral campaign that yielded solid numbers of dedicated fans and press. Sensing the promise of Radiohead’s pay-what-you-want release for In Rainbows (which some claim Reznor suggested to them), he recommended a similar technique to Saul Williams, whose album The Inevitable Rise and Liberation of Niggy Tardust he helped produce and promote. Now, he’s evolved the system for his own use with his new album, Ghosts I-IV, released online this past Sunday with no one the wiser about its impending arrival, save for a few ominous “SOON” messages on his blog.

Ghosts I-IV is a departure from Reznor’s standard for two major reasons. Firstly, this is Reznor’s first collaborative album. Past Nine Inch Nails albums were mostly written solely by Reznor, with a handful of songs that credit others here and there. Ghosts I-IV was written entirely with Atticus Ross, who’s been working with Reznor in various ways for the last seven years. The second major change is that Reznor restricted the period of the album’s creation to 10 weeks, a bold move for a man who’s notorious for taking several years between completed works (the two years between With Teeth and Year Zero was the shortest — on average he takes four or five).

Though the modus operandi might have been different, stylistically Ghosts I-IV will sound vaguely familiar to Nine Inch Nails fans and soundtrack or movie score aficionados. The 36 tracks consist of instrumental, ambient pieces played on some combination of piano, guitar or marimba and a few other ethnic instruments, creating a very cinematic element at times. Occasionally it kicks into electronic industrial moments, as if to remind the listener what or who they’re listening to.

Nine Inch Nails, “2 Ghosts I” (download)

Those scratching their heads at an ambient, acoustic Nine Inch Nails album should know, though, that this is not unfamiliar territory for Reznor, who was a piano prodigy at the age of five. The biggest hint he’s left to this time of his life is Still, the companion album to And All That Could Have Been, which features pared down versions of assorted Nine Inch Nails songs.

The moments that stand out on Ghosts I-IV are those like “12 Ghosts II” and “20 Ghosts III,” which artfully slide between piano melody and heavy electronics. It’s not the kind of album suited to pointing out individual tracks, however. The tracks are short and all four movements take just under two hours. It’s best digested as an entire body of work, the kind of album that’s good to put on one night, sit down with a friend and a bottle of wine and just listen to it. The pacing is a bit uneven, but it makes sense why — Reznor likely wanted to avoid the redundancy that might arise from putting similar tracks together. Staggering the songs with a different mood keeps the album engaging enough to not resign it to becoming boring backing music.

Nine Inch Nails, “12 Ghosts II” (download)

As a whole, Ghosts I-IV plays like a Tarantino’d instrumental retrospective of the Nine Inch Nails discography thus far. Though it lacks the excitement of Reznor blazing down an entirely new path aesthetically, it’s different, pleasant and easily re-playable, and therefore definitely worth owning — and not just in the free form, which is limited to just the first of the four sections. Five dollars gets you all 36 tracks, a considerable bargain in today’s dollar-per-song music economy.