How do you get to Madison Square Garden with Dead & Company? Practice, practice, practice...

Rumors of a post-Fare Thee Well incarnation of the Grateful Dead have been around since the original trio of shows featuring Phish’s Trey Anastasio were announced back in January, but today’s Billboard exclusive confirms it: the band will play on, with members Bob Weir, Mickey Hart and Bill Kreutzmann being joined by John Mayer on guitar and Oteil Burbridge on bass.

Dead & Company will make its debut at New York’s Madison Square Garden on Halloween (Oct. 31), bringing to reality months of wishful thinking for Mayer. The Grammy-winning singer and songwriter is relatively new to the Dead, but his discovery of the band’s 50-year catalog has prompted him to dive deep into the music.

Speaking to Billboard the day before Dead & Co. was announced, Mayer waxed philosophic on the band’s legacy and how he came to represent a new generation of Deadhead.

You discovered the Dead in 2011, how?

I think Pandora was to thank. It was kind of a blind taste test -- a station that wasn't far genetically from the Dead played “Althea” and I heard this riff and went, “What's that?” I actually came in from being outside in the pool, I was dripping wet and had to see what was on the iPod. From there, I went [on] to know a few songs and started recognizing pieces of songs … I feel like my generation also has SiriusXM to thank. The Grateful Dead station on Sirius is its own experience, especially if you drive. If you live in Los Angeles, it's such a brilliant way to score the commute. That was my entrance into it -- how you could cut across town and sit there in traffic and listen to a dozen classic rock songs or you could just sort of drift and watch the sun go down or look at the billboards and take it in on a really abstract level.

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So was your entree mainly through live recordings?

A little bit. I stayed on Sirius for a really long time -- years. And I remember downloading every Dick's Picks from iTunes. It’s actually the only [music] on my iPhone, everything else is on the cloud, but it's the only hard reference I have. I approached the Dead from a completely different angle than most people who are older than me because I kind of represent this new generation of future Dead fans [who came into it] by way of the music only.

Can you elaborate?

I don't know what those [Dead] shows were like. I have Fare Thee Well to give me a pretty good example, and I can kind of reverse engineer what it felt like, but then again, I'm sure I can't. So I represent this generation of listener who didn't go to those shows. There was no sensory bonus for the music. I don't know how much a T-shirt was or who made the best chili. I don't have any of that fan show-going experience so I really discovered the music on a totally pure level. … I didn't come it from the experience of “a friend brought me to a Dead concert in 1987 and I had the time of my life.” I came at it, like, this music transports me to a place in my own imagination.

I hate to sound artsy-fartsy but it becomes your happy place and that's going to be the way people discover that music. And isn't that great that it can work that way? You don't have to be distracted or have other senses working -- you can just listen to the music. And the music stands up because it got me.

How did conversations of possibly playing with the band first start?

In late January, I was at Capitol Studios working on an album, and Don Was, who was present making [2012 album] Born and Raised and [2013's] Paradise Valley with me while I was really falling under the spell of the Dead, was meeting with Bob and Mickey in his office [at Capitol Tower] and invited me up. I couldn't resist, and I sat down and sort of professed my love. I told them how this music had hit me. I wanted to tell them how much it meant to me [seeing as] I have no cultural tie-in with the music -- no preexisting condition, as it were -- and this music just knocked me out. I told them that those songs take me to places I've never been to that I visit daily and I love going there. So I sort of gave a sermon: these songs are for people who have homes who every once in a while don't want homes. And I think Bob said to me, “Hey, you wanna do our PR?”

When did talk of actually jamming come around?

Bob said, “What are you doing first week of March?” My answer: whatever you ask -- that simple.

How did the first jam sessions go?

We all knew when we got in a room and started playing, there was a vitality to it. I learned five or six songs just to have enough under my hands, and even with me sort of bumping into walls musically, there was meaning to it. Something about it was valuable.

What happened to the album that was in progress?

I kind of shifted focus from the record I was making to having a head start on knowing these songs. I was more than 50 percent sure something would come out of it, so I changed course in April, left the studio and dimmed the lights on my album and stuck to pretty hardcore practices that I'm still in now -- not just how the songs go, but how to play them.

How deep did you go?

I'm going pretty deep. I've been going for a while and it has been such a joy to go back to playing guitar for 4 to 5 hours a day. It’s been 15 years since the last time I sat in the room and just tried to get better at playing. It's what I've called Grateful Dead University. It's like a study abroad -- a totally immersive course and a real self-driven scholarship.

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What was your process in wrapping your head around these songs?

It's a lot of guessing and checking and listening -- trying to figure out left brain, right brain, lizard brain, aware brain. If you go too left, it gets a little too nerdy. Too right, it gets a little too abstract. You go to engineer brain and you're not really playing like you. The challenge and what I love about this is figuring out what in the guitar playing is compositional and important to the song and what is someone’s fingerprint -- what is Jerry Garcia's fingerprint. … For me, it’s about finding an authentic space between how I play the guitar and what my instincts are and what these songs are at their core.

Speaking to Bob, Mickey and Billy, they each gave you a lot of credit for being a driving force in making Dead & Co. come to life…

They’re being generous. This wouldn't have happened if they didn't want it to. If I had anything to do with it, it was just not letting deadlines pass.

They also all seemed to agree that you bring a freshness to the music, having not experienced the Dead live before Jerry died….

I think that's the way music stays alive -- young artists come in and reinterpret it a bit. The most futuristic thing you can do in 2015 is play “Ramble On Rose” in the sprit in which it was conceived. That's futuristic because my generation doesn't have that. The catalog might be the most diverse, hard-hitting, powerful and important collection in the history of any band. As a fan, and being a musicologist in my own stupid little way, if you really look at it, it's a Library of Congress of great songs. It's a universe of great songs.

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Now that you’ve gotten to play a wide range of songs, do you have any favorites?

I’m partial to the songs with the great R&B influences in them. “Sugaree” is the song I play for people. Also “He's Gone,” “They Love Each Other,” "Loser" … those songs that share the genetic code of The Band, Crosby, Stills & Nash and Bob Dylan.

Were there songs you struggled with?

I've got what I call the double black diamonds. There are [songs] that require me to learn how to be a better guitar player. “Slipknot,” for example -- if I tried to play it now, I couldn't do it, so it's forcing me to be better. Also, if you're doing everything right, you get it wrong. I don't want to sit with an architect's pencil and a T-square either. I think a little bit of drift is good for anybody, and I suspect there will be purists on a guitar level who'll go, “That's not the way.” But you carry it forward by drifting.

What did you think of Trey’s performances at Fare Thee Well?

I thought Trey was great and I was so proud of him as a guitar player. People don't understand what he did -- he spent months practicing, drilling on the guitar to play every song one time. He ostensibly isn't going to play those songs again but he gave it the effort of an expert professional musician. The other thing that was so brilliant was that he was such a tasteful player. He found his spot, his zone, right from the beginning.

Some said — Billboard included — that it took him a minute to find his footing.

I think there was a confidence thing that happened but he was so respectful. I said to a friend, there are probably 6 or 7 guitar players in the world who could've done that show. The elephant in the room is that you're playing the music of this phenomenally talented guitar player in Jerry Garcia, who, on a technical level, was just unbelievable.

What you want to do as a musician is make people feel safe. Like, “I won't be needing to clench my fists here.” Trey became just a conduit for all of that music and with it had great phrasing, articulation, natural timing. He did something incredible to the legacy and didn't leave it any easier for me to pick up the baton. I consider myself no different than any other fan. I don't think I've had a more profound experience than anybody else discovering this music except that I have this reach on the guitar.

You attended all five Fare Thee Well dates, was the experience what you imagined?

It was thrilling and I have never felt that before. The feeling came over me -- I was in Santa Clara and I went, “This can't be over.” The way I look at this is carrying that spirit forward. I feel like it's the responsibility of any musician who cares to not let great, important music die. There's a lot of people who don't know what that music is yet because they weren't exposed to it culturally. They don’t know that there is that swing and that groove you need in your life. Being a deadhead or being a fan of the music sits completely separate from any other walk of life you may identify with. That means everybody can feel this pulse. It's about carrying this music forward because these songs will change your life.