Mos Def changed my life, and now it's over.

A sentence like that can come across as a lazy cliche, but in this case, it's quite literally true. I now write about hip-hop for a living, it was Mos Def who first showed me just how breathtaking this culture could be, and now he's pulling the plug on a uniquely remarkable career. Last night, in a message on KanyeWest.com, Yasiin Bey (as Mos Def changed his public name to in 2011) said that he was done with the music and entertainment industries, "effective immediately," and would be releasing one last album later this year as a parting shot/gift. And so I did the only thing I could think to do with news like that; grab my headphones, put on Black on Both Sides and start writing...

When I first entered the hallowed halls of high school my hip-hop listening habits came almost exclusively by way of the mainstream. Jay Z, Biggie, Nas, I had all the obvious albums from all the obvious names, all rappers I first heard on MTV. But by my sophomore year Lyricist Lounge and Soundbombing tapes had served as a red pill into underground hip-hop, and right as my mind was just beginning to be blown, Black Star dropped and shattered my cranium with a sledgehammer. Kweli was the muscle of the duo, Frazier crumpling opponents under a steady hail of blows, but Mos Def was Muhammad Ali, floating, stinging, as soon as you thought you had a handle on him he'd disappear, only to re-emerge from some unknowable angle with an overhand right. I still don't know if I've heard anything as simultaneously beautiful and devastating as Mos' hook on "Respiration."

So much on my mind that I can't recline / Blastin holes in the night til she bled sunshine

Breathe in, inhale vapors from bright stars that shine / Breathe out, weed smoke retrace the skyline

Heard the bass ride out like an ancient mating call / I can't take it y'all, I can feel the city breathing

Chest heaving, against the flesh of the evening / Sigh before we die like the last train leaving

How is it even possible that those words came from a human mind? And just when I had memorized every word of Black Star, Mos delivered his solo album Black on Both Sides. That album was a revelation, and not in the way the word's commonly used, I mean in the Biblical sense; Black on Both Sides was a heavenly being's disclosure of Himself and His will to the mortal world.

This was before Spotify, before entire music collections were enclosed within a phone, when the CDs you had in the car were your only source of music, and month after month I only had Mos Def in my car. By the time summer hit I had played it so many times I passed the time at my soul-grinding summer job by seeing if I could recite every word of the album perfectly in my head. I laughed at the "ass so fat you could see it from the front" line every time I listened to "Ms. Fat Booty" and played "Mathematics" so many times DJ Premier's scratches began showing up in my dreams.

I hate to use terms like "underrated" because while Mos Def never achieved the same levels of commercial success as many of his less-talented peers, that's because he so purposefully existed outside commercialism. Why didn't Black on Both Sides go platinum? Probably because hordes of teenagers weren't exactly begging their parents to buy an album filled with songs about water pollution and slavery. Still, Black on Both Sides deserves more praise than it gets, I'll go to my grave arguing that it was both outstanding and subtle, and it was also powerfully influential. Drake's fans may think that Aubrey Graham was the first rapper to also sing, but Umi says that claim is laughably false.

In retrospect, I've seen Mos Def's retirement coming for the better part of a decade now, frankly, it's only surprising it took this long. Almost as soon as he released Black on Both Sides Mos Def became increasingly uncomfortable confined to a life spent labeled as a rapper. His next album, The New Danger, found him veering away from hip-hop in an attempt to reclaim rock as a Black music, then a combination of acting pursuits and a growing disdain for the music industry found him releasing only one more album in the last ten years, 2009's The Ecstatic. And just like that, short of the occasional Chappelle Show freestyle, Black Star reunion and assorted loosies, a man who could have contended for the best rapper alive title if he'd been driven towards such acclaim had effectively stopped rapping.

Rappers, like boxers, are notorious for leaving a broken trail of retirement promises in their wake. As exhausted as they may be by the music industry, money and public adoration are hard drugs to quit cold turkey—life starts feeling uncomfortably quiet when you've spent years living for applause. But Yasiin Bey is hardly JAY-Z, promising himself he'll walk away after he does this one last show at Madison Square Garden. Bey has slowly but steadily removed himself from music for years—you don't spend the last six years living in South Africa with your family if you're at all interested in rap star status. And so this last album will almost assuredly be his actual last album, and truth be told, no matter how great it is, I expect it to sound like a funeral march to me.

Yasiin Bey the person isn't dead, and he isn't dying, but his retirement marks the official death of Mos Def the rapper, the musician, and so like any death, it's cause for both celebration and mourning. I've been listening to Black on Both Sides again while writing this, and it's more than an album, it's a time machine. My whole life is wrapped up in that album, and so the man who made that album retiring feels like a part of my memory is being retired as well, and that's an uncomfortable feeling.

It feels like the breakbeats you get broken with. It feels like the pain of too much tenderness. It feels like the sigh of the last train leaving.