Some bands have a sound, some have a look, others a strange allure you can't quite explain and, in rare cases, all three.

[artist id="1009"]R.E.M.[/artist] were one of those bands. The long-running alt rock godheads who [article id="1671138"]packed it in after 31 years[/article] on Wednesday (September 21) will be remembered for a lot of things by a lot of the people who bought millions of their albums. But I'll remember them best for the consistent, exquisite confusion they sowed.

It's hard to put your finger on how this strange brew came to define the alternative-rock era of the mid-1980s and early 1990s. Peter Buck's iconic, chiming, Byrds-inspired guitars -- which came to be known simply as his signature "jangle" -- bassist Mike Mills' flawless high harmonies and Nudie-suit style, original drummer Bill Berry's economic, steady-on drumming and singer Michael Stipe's cryptic ... everything.

This was a band that should have had no chance of becoming what they did. They were too odd, too hard to unpack. From day one, contemporaries like U2 had soaring rhetoric and urgent arena-reaching power that seemed destined to conquer the world through a combination of ambition, chutzpah and titanic riffs.

But R.E.M.'s alchemy was darker, not as immediately obvious, which is what made all the difference. They literally made no sense. From their 1983 full-length debut, Murmur, through to their final, 15th album, this year's Collapse Into Now, Stipe's lyrics were like Zen poetry: knotty, stream-of-consciousness and thought-provoking in a way 99 percent of rock music never is, or was. You couldn't sing along because half the time it was hard to hear what he was even saying. And when you did find out, the Rubik's cube just spun again as you tried to decipher what he was all about.

R.E.M. made you work for it.

It didn't matter if you were inspired enough to dig into their muses, which ranged from beat poets and mad literary ravers like William S. Burroughs to punk godmother Patti Smith and the Flying Burrito Brothers, or just let their music wash over you. The end result was that you left with more than you came in with.

Even when they hit the sweet spot with hits like "Everybody Hurts," "The One I Love," "Shiny Happy People" and the multi-VMA-winning "Losing My Religion," R.E.M. challenged you in other ways, through arty, envelope-pushing videos.

I got the chance to interview the band a number of times in the mid- to late '90s and early 2000s, and I probably worked harder preparing for those chats than for any others I'd done before or since. Because, like in their music, R.E.M. tested you in interviews. They didn't give pat, pre-planned answers. They fired back honestly and unflinchingly when it felt like the questions were unfair or slanted and always focused on the one thing that mattered most to them: the music.

With few exceptions, you didn't read tabloid reports about the personal lives of the group's members, their finances or Hollywood exploits. Mostly that was because there weren't any tales to tell. The stories were all there in the grooves, in songs like "Talk About the Passion" and "World Leader Pretend."

Their inner circle was a trusted group of friends and advisers that changed little over the years, one they treated like family. They were also one of rock's most politically and socially literate groups ever, supporting everything from PETA to Rock the Vote, environmental causes and human rights.

R.E.M. showed the world, and such acolytes as Nirvana and Pavement, that you could stick to your guns and keep making the music you heard in your head even if it wasn't fashionable -- especially if it wasn't fashionable.

Talk about the passion.

Share your favorite R.E.M. memories in the comments below.