It's not very often those who work behind the curtain of the music industry are referenced in songs, let alone in album titles. But that fourth wall was breached on July 14, 1998, when the fifth Beastie Boys LP, Hello Nasty, was released. While the reference might have flown over the heads of most fans, the name was a winking nod to the group's longtime publicity firm Nasty Little Man and their salutation when people called the company.

"This goes back to the days when business was transacted primarily over the phone," explains Nasty Little Man CEO and owner Steve Martin, whose ties with the Beasties go back to the hardcore days when Martin was a member of Agnostic Front. "The greeting was the creation of Toco Hara, who had come over from Japan to work for us. She had problems with the word 'little' and one day just spontaneously started answering the phone with a manic 'Hello NASTEEEE!' and we all loved it, not least of which all three Beastie Boys who called the office frequently, both on legitimate business and also pulling hilarious pranks."

The christening of the album wasn't the only convention defied on Hello Nasty. At 67 minutes and 22 tracks, it stands as the longest Beasties album in their catalog. What Mike D, MCA and Ad-Rock stood for as one of the premier rap acts of the day was exemplified on such crowd faves as "Remote Control," "Body Movin'," and lead single "Intergalactic." However, what really helped to make Hello Nasty stand out were the directions the band was going beyond the realm of hip-hop in 1998. Lyrically, Mike Diamond, Adam Horovitz and Adam Yauch were harking back to the Treacherous Three-era of rap, but on an instrumental level the group was eager to explore sounds and styles beyond the scrappy hardcore and Blaxploitation soundtrack funk of 1992's Check Your Head and 1994's Ill Communication.

"It was the beginning of the final phase, which is something that can only be said in hindsight I believe," explains Martin. "If you look at phase 1 as the early punk/hardcore Rat Cage Records stuff, phase 2 as the Def Jam 12-inches and Licensed to Ill, phase 3 as the move to California that produced Paul's Boutique, Check Your Head and Ill Communication, then phase 4 kicked off with Hello Nasty's return to NYC and progressed through To the 5 Boroughs and Hot Sauce Committee Part Two. It's such a New York-y record. It feels like the musical equivalent of a mid-July humid, sweaty but ultimately joyous all day subway ride from the Lower East Side through the Village to Harlem and the Bronx out all the way to the eastern reaches of Queens back through Brooklyn, with stops to sample everything every neighborhood had to offer."

One of the boldest juxtapositions on the album happens towards the end of its runtime, when they become entangled in a soundclash with dub-reggae icon Lee "Scratch" Perry on Nasty's penultimate track "Dr. Lee, Ph.D", which was a collaboration aided by keyboardist "Money" Mark Ramos-Nishita's established rapport with the quixotic producer.

"Of our whole crew, I was closest to Mr. Perry," explains Money Mark. "I understood his vibe and where he was coming from and was able to 'translate' what he was saying and we both used the shit out of the Teac 3340 four-track reel-to-reel. The Beasties adored him. Put him on the cover of Grand Royal magazine and effectively re-launched his career. Perry came to the studio and put down some vocals in about five minutes. Never had anything written in paper. Just doing some stream-of-consciousness vocal spewing."

"I'll never forget that day Lee 'Scratch' Perry came by my place," says Sean Lennon, whose 1998 debut album was released on the Beasties' label Grand Royal. "He's kind of like a shaman, like a wizard, right? And I was young enough that he scared me a little bit. I remember he wrote all this stuff on this poster and taped it up on the wall. And he was like, 'Yah have to keep that on your wall; if you ever take it down there, bad things will come to ya!' So I framed that shit and never took it down until I moved. But I still have that fuckin' poster."

Speaking of Grand Royal, which they had launched in 1992 as a means to help gain exposure to such friends as Luscious Jackson and DFL (Ad-Rock's hardcore side project), it had reached a peak in its mission by 1998 with the signing of Lennon, digital hardcore pioneers Atari Teenage Riot and Buffalo Daughter to an already impressive roster that also included Ben Lee, Ween and DJ Hurricane. And that's not to mention the crew of prolific people they ran with once back in New York, establishing a posse of like-minded Downtown NYC folks like Cibo Matto, the Jon Spencer Blues Explosion and Sonic Youth, with whom they were able to freely exchange ideas and concepts.

"When they moved back to NY from Los Angeles, they surrounded themselves with all of these creative musicians and writers and filmmakers," describes former Grand Royal label manager Natalie Carlson. "We had the clothing store, the magazine, the record label. The Boys were doing everything they wanted with people they wanted to work with. It was very communal."

Instrumental tracks like "Song for Junior" and "Sneakin' Out of the Hospital" -- which prominently featured the Beasties' new DJ, Bay Area turntablist Mixmaster Mike (whose audition via phone is featured in the intro to "Three MC's and One DJ") -- further enhanced the group's appreciation for television soundtrack music from the '70s.

"I'm a big fan of 'Sneakin' Out of the Hospital,'" admits the band's longtime producer Mario Caldato, Jr. "That was done at Sean Lennon's rehearsal studio. We got a really beautiful, fat tone in that room. That song was one of my favorites, and I was glad to hear it recently when I was in France on Radio Nova. It was a joy to my ears to hear a deep cut like that on the radio."

"They wanted to change it up," Lennon tells Billboard. "I remember Mario brought a portable studio into a room in my house and they just made the record there. It was awesome. I remember being there when Ad-Rock was using the Vocoder for 'Intergalactic.' He wound up using a silver Vocoder type thing. I had my dad's Vocoder at my house and we tried to get it going, but it didn't work."

Then there's "Song for the Man." The first of three songs on the album to feature sung vocals by Horovitz, it's one of the most uncharacteristic tracks of the Beasties' signature style, coming across like a fusion of Esquivel and Syd Barrett-era Pink Floyd that touches upon the sense of enlightenment all three Beastie Boys were feeling as they were getting older, wiser and more activist-driven as curators of the Tibetan Freedom Concert festival. But the intensity of the lyrics, however, suggest "Man" could have very well been a hardcore track in a previous incarnation.

"'Song for the Man' is an angry song packaged in a slow, circus-y, psychedelic groove," proclaims Nishita about one of the four Hello Nasty tracks he appears on. "It's really a #MeToo movement tune. A Beastie ethos of anti-bias practices and reinforced by Kathleen Hanna's closeness to Horovitz. These were the years of Beasties enlightenment and political activism. So proud to be part of it. In fact, that year Adam Yauch spoke his mind about non-violence and anti-bias on national television."

Horovitz further showcased the surprising range of his singing voice on the wobbly "And Me" as well as the album's haunting final cut, "Instant Death," written in tribute to David Scilken, who fronted Ad-Rock's high school punk group The Young and the Useless and passed away from a drug overdose in 1991, as well as the rapper's mother, Doris Keefe Horovitz, who died shortly before the release of Licensed to Ill in 1986.

"It would have been nice for her to be alive and to see some of the stuff that I've learned," Ad-Rock told Rolling Stone in 1998, in regards to how far he had come from the nasal-voiced brattiness of his prefab days. "She always knew there was more going on with me than just being a fuck-up. And it would have been nice for her to see that she wasn't just dreaming that up."

"At that point we all had these little 8-tracks and Adam had set his up at their little rehearsal studio," Caldato explains. "They'd all come up with these little ideas in demo form and would present them to the group. Adam was the busiest and he came up with a ton of ideas. But that song, 'Instant Death,' in particular, was very personal and he put a lot of emotion into it. I think he wanted to put it out there. We heard it and we all thought it sounded unlike anything the Beasties had ever done. It was very heartfelt and unique, and he came up with the whole thing himself, recorded it on his own and mixed it and everything. It came out very delicate sounding but also had an intense feel to it as well. I think it was a good closer for the record, because it's a pretty intense album."

The most poignant dynamic shift on Hello Nasty, however, comes 15 songs into the album with the song "I Don't Know," a tender bossa nova ballad sung by the late, great MCA with a tenderness and vulnerability that stands in firm contrast to the gruff-voiced braggadocio of his rapping.

"I still have the lyrics sheet of 'I Don't Know' in my memory box," explains Cibo Matto's Miho Hatori, who sang backup for Yauch on the tune, in an email message to Billboard. "Adam's handwriting always brings back the memory of that moment in the studio, vividly. He was very calm in the studio and handed me the pencil, with a hand written lyric sheet. I had nothing to say except YES because it is just full of Adam Yauch in it. What I could do was just sing the melody and no words -- it was already like a pure gem in the rough. He was the kind of person who was transparent about himself, had no fear to show his soul-searching in his life in that time. He was open to share with us. I think Adam's spirit lives in the lyrics of that song. I really have a huge respect to Mike D, Adam Horovitz and the producer, Mario Caldato Jr. who finished the song to be the way it is. I'm so blessed to be a part of such a beautiful song!"

"While we were working on Hello Nasty I was listening to a lot of bossa nova. Mario [Caldato] is originally from Brazil and he knows quite a bit about '60s Brazilian music," wrote Yauch in the liner notes to 1999's Beastie Boys Anthology: Sounds of Science. "He turned me on to a number of things, but in particular, I couldn't stop listening to both Jorge Ben and Antonio Carlos Jobim. At some point when I was listening to Jobim's 'Aguas De Marco' I decided that I wanted to write and record a couple of bossa nova songs. I guess that's kind of like saying 'I was watching Michael Jordan play basketball and I decided that I want to play for the Bulls.' Sure you do."

Upon its release on July 14 in 1998, Hello Nasty was met with largely lauding reviews and debuted at No. 1 on the Billboard 200 album chart. But while it was largely those tasty summer jams peppered throughout Nasty that cemented its success, when thinking about this record 20 years later, its lasting legacy exists not in the rhymes, but rather in the spirit of adventure the Beasties cultivated.

"It was a really amazing time, and I don't think I realized because I was so young that life wasn't always going to be that way," proclaims Lennon. "I felt like I was part of a community of musicians, and some of my closest friends back then were really successful artists and felt like I related to them as people. And it seemed like kids my age were all interested in open-minded music. I like to call the Beasties the Beastles, because for my generation going from their early records to Paul's Boutique then Check Your Head and Ill Communication and then Hello Nasty, the only experience I can compare to what it might have been like was The Beatles going from Rubber Soul to Revolver to Pepper to The White Album. I can't think of any other group who opened my mind up to music as much as the Beasties did. I was so lucky to be signed to Grand Royal and get to hang out with those guys. New York, at that time, it just seemed like that's how it always was going to be. It was a golden moment."