A$AP Rocky's new album, At.Long.Last.A$AP, features a number of notable contributors. M.I.A., Future, SchHoolboy Q, Kanye West, Juicy J, UGK, Mos Def, Danger Mouse and Mark Ronson – the list is like a Rolodex of hip-hop's best-known talent. Then there's Joe Fox – a man who appears a staggering five times on the album – and who we'd hazard a guess most people would struggle to identify on the street if he were standing there, right in front of them, wearing a T-shirt that said "Hi, I'm Joe Fox."

So who is this mysterious singer/songwriter with the modest web presence and zero pre-existing hip-hop credentials? Here's what we do know.

He met A$AP Rocky on the streets in London.

According to GQ, "We were literally wandering the streets at 4 a.m. on a Tuesday and this guy walked up holding a guitar," says Rocky's longtime collaborator Hector Delgado of Clockwork Studios. "Fox played them a song, and now he pops up all over the new album."

As Fox himself notes, "I had nowhere to live in London so I was selling mixtapes of my music anywhere I could so that I'd have money to live somewhere. I was doing that for a while, and I was making quite good money. So I'm on Wardour Street and I see this guy – I don't know who he is 'cause I don't listen to new music – and he's with this other guy who turns out to be Hector Delgado, who's produced a lot of songs on Rocky's album.

"I go up to them and say 'Do you want to buy a CD' and Rocky says, 'Can you play me a song'. So I play a whole song and I get to the end – that's usually when people buy a CD – so I say 'Do you want to buy a CD?' and he said 'No, but we're going to Starbucks, and then to the studio, you should come and work with us. Jump in the car'. So I got in the car and he says, 'My name's A$AP Rocky, you've got an amazing sound, lets record together.' So we did. I checked out his stuff later that week and I quite liked it, which I wasn't expecting, because I don't like much modern music. I really liked Long.Live.A$AP."

He described At.Long.Last.A$AP in three words.

In speaking with Hattie Collins at London’s St. Pancras Renaissance Hotel, he called A$AP Rocky's album, "psychedelic, forward-thinking, and a masterpiece."

The first song they recorded was "Max B" which made the album.

"It's about the situation he's currently in [Max B was sentenced to 75 years in prison on murder conspiracy and kidnapping charges that he heavily denies], Fox told i-D. "I can't say too much, other than the song is amazing and Rocky asked me to write a chorus about the situation and that's what I did. Rocky told me the story and I just wrote about it."

Ahead of the album's release, check out the 10 things you should know about A$AP Rocky. Afterwards, watch the trippy video for "LSD."