Ænima is the album most Tool fans probably consider their most classic, it's the perfect middle ground between their more aggressive earlier material and their more experimental later material, and if you ask me, it's the best place to start with Tool. It's also the first album with bassist Justin Chancellor, who cemented the lineup that Tool have today, and their first of two consecutive albums with producer David Bottrill, who co-produced King Crimson's '90s-era classic Thrak a year earlier.

Coming five years after Ænima, 2001's Lateralus is Tool's most experimental album. It still has moments that qualify as metal but it's overall a progressive art rock album that puts the band's King Crimson, Pink Floyd, and Rush influences more in the forefront than any of their other studio releases. On this album, long songs are more the rule than the exception, and it's heavy on atmosphere and ambience; the bulk of it would probably appeal even more to post-rock fans than it would to people who came to Tool via their adjacency to nu metal. To revisit the Nine Inch Nails comparison I made earlier, Lateralus is sort of to Ænima as The Fragile is to The Downward Spiral. In both cases, the latter is more classic, more widely loved, and more radio friendly, but the former is adventurous in ways that early fans of the band may have never predicted. A song like Lateralus' "Reflection" sees Tool fully off in outer space, with words seeping out of Maynard's mouth like a slow leak as the band builds an atmosphere rather than focusing on riffs or verse-chorus-verse song structure. It's closer in spirit to Hawkwind or spacey Grateful Dead jams or certain songs by the aforementioned Pink Floyd than it is '90s alt-metal, and it's far from the only time that Lateralus explores that kind of territory.

It was a bold move for Tool to make an album like this; five long years go by after a breakthrough album and they come back with 79 minutes of exploratory jams? It must have pissed a lot of people off, but it was a crucial step in establishing Tool as a band who sets no limits for themselves and insists on pushing forward. Lateralus is uncompromising in its experimentation, yet it remains just as gripping as the band's more accessible albums. Lateralus was the album that proved Tool could make just about any kind of music they wanted, and still sound like Tool. That's a sign of a truly great band.

It's probably safe to say that, upon release, 10,000 Days got more of a lukewarm response than its predecessors. It wasn't a return to form, but it was a return to being a lot more accessible than Lateralus was -- be it the wait-this-is-actually-kinda-nu-metal chugs of "Jambi" or the prog-pop of "The Pot" -- and I could see someone making the argument that, unlike every Tool album before it, it wasn't a massive leap forward. But year after year went by without a followup, and as is often the case when a band gives their fans that much time for a "divisive" album to sink in, eventually people start to realize how brilliant it is. That was very much the case with 10,000 Days, which seems silly to be critical of now. In its own way, it's just as essential as everything that Tool did before it. Many of its songs are staples of Tool's current live show, and those songs sound as great as the classics. And when you've got a band as unique and larger-than-life as Tool, sometimes you set your expectations super high for each new album, but a little distance can remind you that even their worst album towers over plenty of other bands' best.

And though 10,000 Days was indeed a more accessible version of Tool, one more similar to the alt-rock and alt-metal bands you could still hear on the radio in 2006, it also had songs like the 17-minute epic "Wings For Marie (Pt 1)"/"10,000 Days (Wings Pt 2)." That song, and a couple others like "Intension," see Tool getting even more trippy and more atmospheric than they did on Lateralus. And even if 10,000 Days wasn't a major leap forward, it still finds ways to not sound like any other Tool album. As a band who's been around for nearly 30 years and released just four full-lengths, we can probably assume that -- like My Bloody Valentine or Portishead or Slowdive -- they've got a serious sense of quality control and won't release something new unless they're absolutely sure it adds to their discography. Let's hope that means the 13-year wait for Fear Inoculum will be worth it.

Tool were often wrongly grouped with cheesy nu and alt metal bands, and a lot of that is because they probably do share more fans with nu metal bands than they do with, say, Radiohead. But there's always been so much more to Tool than the Headbanger's Ball-friendly songs; their psychedelic, atmospheric parts do have more in common with Radiohead (or Pink Floyd or King Crimson) than with metal, so it makes sense that people like Parquet Courts' bassist and Grimes are big fans. The more atmospheric, art rock side of Tool was stirring beneath the surface on Ænima, was embraced pretty strongly on Lateralus, and poked its head out a few times on 10,000 Days, but Fear Inoculum is the first time Tool have made an entire album focused on this side of them. There's not a single song that you can really call metal until the very last track, "7empest." Instead, Tool favor clean guitars, clean vocals, psychedelic electronics (courtesy at times of Lustmord), and meditative passages that gradually pull you in rather than hit you with instant satisfaction.

It isn't totally surprising -- Maynard James Keenan has talked before about preferring to play less metal material and Tool have made music like this before -- but it's still kind of badass that Tool would steer clear of their most crowdpleasing elements on the album that they made their fans wait over a decade for. It doesn't feel like trolling though, it just feels like Tool making exactly the album they want to make regardless of what anyone expects of them. There are a few kinds of albums that we tend to see artists make after a long wait like this: sometimes they return to their most classic and beloved sound, sometimes they pick up right where their most recent album left off, sometimes they make an album so bad you wonder why they bothered to come back, and sometimes they make the album that it seems like they wanted to make for most of their career, yet for whatever reason, never did. Fear Inocolum feels like the latter. You could tell from Lateralus that Tool wanted to make an album like this, but Lateralus didn't go all in on the clean, ambient sounds the way Fear Inoculum does. That album still had enough of a radio-friendly alt-metal side to maintain Tool's status as a force in mainstream rock, but on Fear Inoculum, they don't sound like they care if rock radio plays any of these songs or not. Especially with every song clocking in at over ten minutes except the psychedelic, instrumental interludes that are sprinkled in between some of the songs.

Fear Inoculum is Tool's most ambient album without sounding too sleepy and their most psychedelic album without sounding over the top trippy. And even though these songs are far from radio-friendly, and require tuning out from everyday life and really listening closely even more than any other Tool album, they reveal themselves to be almost as catchy as Tool's biggest hits. The hypnotic riff and the satisfying chorus of the title track, the little "become pneuuu-MA" in "Pneuma," the "warrior..." hook in "Invincible," the circular guitar patterns in the pre-chorus of "Descending" -- they're all just about as earwormy as Tool's biggest hits. And it's impressive how naturally these songs earn their lengthy running times. They're not grueling to listen to or overstuffed; they're over 10 minutes each because that's how long they need to be to get their point across, but they never overstay their welcome. When you get to the metallic album closer "7empest," which is easily the most accessible song on the album, it doesn't feel like the climax that Fear Inoculum had been building towards; it feels more like a satisfying encore to an already-great show.