Rick Rubin is the latest industry insider to join the hive mind that is Genius—aka Rap Genius under its new, all-genre-encompassing, Sasha Frere-Jones-edited direction.

The start-up has dropped the “Rap” from its title as part of its ambitious aim to “annotate the world,” starting by bringing in super producer and Def Jam founder Rubin to annotate some of his favorite songs. This includes giving behind-the-scenes details on tracks that he produced—like “99 Problems,” where he says that Jay’s second verse was “that first time I ever saw him write anything down”—and fanboying out over tracks that he just likes, such as James Blake’s “Retrograde” (“James Blake is spectacular, I love him all the time”).

Read a couple of the highlights below—including confirmation that an “alternate version of Yeezus” exists(!)—and head to Rubin’s Genius profile to read all of his contributions in full.

“Rock Hard” by Beastie Boys

I cleared the use of “Back In Black” with AC/DC and they loved it.

But this was in the days where no one knew what sampling was. I remember playing it for Malcolm Young on headphones backstage at an AC/DC concert, and he was like, “Who played guitar on that?” And I was like, “I did.”

I mean it’s a combination — there’s samples involved too, but I’m definitely playing. And I programmed the drums. You couldn’t do it today.

“99 Problems” by Jay Z

Jay came into my studio every day for like a week, I kept trying things that I thought would sound like a Jay record, and after like three or four days he said, “I want to do something more like one of your old records, Beastie Boys-style.” Originally that’s not what I was thinking for him, but he requested that vibe, and we just started working on some tracks.

Musically, there were a couple of different ideas that [engineer] Jason [Lader] and I were working on independently that we played back together, and the way the beats overlapped was really interesting. It wasn’t planned out, it was more experimenting.

There was a part where it really sounded crazy and the beats were fighting each other. Jason was operating the Pro-Tools, and I’m saying “Move to the left, move to the right, try this beat, add this, do this,” and then he makes it do it. There’s nothing live on the track.

It’s a combination of three samples — “The Big Beat” by Billy Squier, “Long Red” by Mountain, and “Get Me Back On Time” by Wilson Pickett — and two programmed beats coming in and out.

“Bound 2” by Kanye West

Something we talked about with Kanye was doing an alternate version of Yeezus,because there are so many versions of songs, great versions. There are versions just as good as what’s on the album, just different. I know as a fan of the album, I’d like to hear that. Maybe some day, whenever he wants. But it exists! That shit exists.

“Only One” by Kanye West

Kanye is a combination of careful and spontaneous. He’ll find a theme he likes quickly, and then live with that for a while, not necessarily filling in all the words until later. At the end, he’ll fill in all the gaps.

He was upset at one point when I said that he wrote the lyrics quickly. He’s right — they percolate for a long time, he gets the phrasing into his brain, lives with it, and then lines come up. It definitely starts from this very spontaneous thing.

On “Only One,” a lot of those lyrics came out free-form, ad-libs. The song is essentially live, written in the moment. Some of the words were later improved, but most of it was stream of consciousness, just Kanye being in the moment.

Lead photo credit: Pascal Le Segretain/Getty Images