This year has undeniably been the year of BTS, and nothing’s proclaimed the act’s ascension to the top tiers of pop royalty more than landing atop the Billboard 200 chart with not one, but two albums from their Love Yourself album trilogy.

The second, August’s Love Yourself: Answer, has spent 16 weeks on the chart as of time of publication, surpassing the record of 15 weeks that May’s Love Yourself: Tear spent on the chart.

A compilation album featuring two discs of music both old and new that completes the Love Yourself series -- which began last September with Love Yourself: Her, Answer -- takes the listener on a philosophical pop journey of self-love, plucking inspiration from a variety of global genres.

Aside from BTS' members themselves, over 20 different songwriters worked on Love Yourself: Answer, including many from North America and the U.K. Over the past few months, Billboard spoke to several of them about their work on songs included on the first disc of the historic album.

Here’s what they had to say, in order of the songs' placement on the tracklist.

Melanie Fontana on Jungkook’s “Euphoria”: I wrote the chorus and parts of the bridge and some of the verses. We ended up making a lot of the changes. [DJ Swivel] brought me in when the song was partially finished and it needed some help. The song didn’t actually have a chorus, so I went in with him and worked. When I first heard the initial sketch, I thought that it could have a more explosive feeling. I thought the chorus could explode more with something chanty that not only the guys in the band could sing, but that people in the crowd could too. I added a bit more of a sing-along vibe. When I heard what the Korean lyricist did I just thought, “Wow, this song was meant for these guys.” I know Jungkook -- I’ve been such a fan of him, I never thought he’d be the one that sang it. But for me, I didn’t know it was going to be as big as it is. I love that they each have their moment to shine [on the album].

DJ Swivel (Jordan Young) on "Euphoria": To me, “Euphoria’” is my personal favorite that we’ve done. “Euphoria” was kind of the first thing that I sent them. It was the song that started our working relationship, so for me there was a lot of personal, sentimental value to that song. To me, what I first fell in love with when I first heard the guitar and piano [from an early version of the song written by collaborator Candace Nicole Sosa]. It’s just such an emotional melody. I always love chord and melodies that feel more emotional. There was this nostalgic sort of vibe to it that I really liked. Being that it was called "Euphoria" I wanted the drop to feel very light, bright, and colorful. The song goes through a lot of different emotions as it grows.

Ray Michael Djan Jr. and Ashton Foster on Jimin's solo “Serendipity,” which was originally featured as the introductory track on Love Yourself: Her but was extended for Love Yourself: Answer:

Djan: We had written a few songs [for Her], “Serendipity,” “Best of Me,” and another song, and we weren’t aware that [“Serendipity”] was just an intro at the time. We had kind of just written a whole song. We were surprised when they came back to us again on this project and said, “Hey guys, we want to make it into a full song.” So that was exciting.

Foster: They had the song title. They gave us, as they do a lot of times, a very deep, meaningful paragraph when they sent the track over about what the track is all about. I remember it was quite in-depth, even about the word itself. The concept was already there. It was a case of just creating a really strong melody, and that’s what me and Ray always think of because we never know if the English words are going to work when it gets translated. We’re very melody strong, and making sure that that works first. And then we fill in the gaps after.

Matthew Tishler on “Dimple,” originally released on Love Yourself: Her: I remember starting a bunch of ideas with friend and co-writer Alison Kaplan in 2016. We kind of started a bunch of tracks, melodies, and song concepts, and we sent the beginnings of this idea, at the time called “Illegal.” RM took over and got involved with the lyrics. We were simultaneously working on the track while they were working on their end, kind of east meets west worldwide collab that took place long-distance, without even meeting the guys. They changed the title but somehow they kept the word “illegal” in the song.

We were trying to do something that felt kind of like a hybrid K-pop and American [pop]. We wanted it to feel like a real worldwide collaboration so used a lot of American Top 40 sounds in the production. I’m not sure that the chords in the harmony are classically K-pop. You know how K-pop is very complex harmonically and there’ll be all kind of interesting chords and complex, jazzy R&B turnarounds. This one, I think, is pretty simple from a chord perspective, so it’s more American in that way. We were trying to think worldwide, bigger than the U.S., bigger than Korea. We were trying to think what could this band do to make an impact for their listeners around the whole world.

Charlie J. Perry on V’s solo “Singularity”: They gave me this amazing brief, kind of, of what they wanted. It was like a poem. They sent me a poem of what they wanted it to feel like, almost. Incredible. I read the brief and it kind of came naturally to me, because it was really emotive. They like Daniel Caesar and said they wanted something along the lines of that kind of neo-soul. Me, I’m a big fan of D’Angelo. I think that kind of feel, that ballad-y feel is very popular right now and people get drawn to it. When they gave me the brief, I thought this is exactly the kind of music I like writing and listening to. I just sat down, played around with a few ideas, tried to get across the emotion that is necessary for a record like that. I wanted to inject something very emotional into it. So drawing on my past experience and relationships not necessarily going the way you expect them to, emotional things I could draw on to create something that, you know, melodically is going to hit home right in the heart.

I think keeping it quite simple is always a good thing to let the vocals shine, because at the end of the day that’s what you’re listening to. The vocalist, the human connection with the song. Keeping the chords simple, creating a lot of space within the production to have the vocals come through and the harmonies accentuate the parts. I was absolutely blown away [by the finished song]. Like [V] really, really connected with it. It was such a beautiful thing because we haven’t even actually met. To send something across the world and for somebody to mirror that with such passion and emotion was such an incredible experience itself. He definitely has the character that this song seemed to gel so well with.

Jake Torrey on the surprise of “The Truth Untold,” originally released on Love Yourself: Tear: I wrote the song with Roland Spreckley, Annika Wells, and Noah Conrad. I think we were actually trying to write for Flume that day, but obviously it didn’t turn out that way at all. We just started playing around with cooler chords. Conrad’s an unbelievable piano player and he had the chords he was sitting on. It sounded like a Sam Smith-y ballad at some point. The original English lyrics had nothing to do with what it ended up with. One line was like, ‘F--- all my friends if you want to but I want you.’ Obviously very, very different than what it became! But yea, we were just trying to write something to pitch for another artist and it didn’t end up being in that lane at all.

I was later working with another K-pop artist Eric Nam over Facetime to finish up one of the songs for his EP and he was like,”Oh, I gotta run but congrats on that BTS thing.” And I was like, “What BTS thing?” And he said, “I was with one of the guys and he played me this song that was definitely you singing on it.” I was like, “I have no idea what that’s about.” I asked around my publishers and managers, but everyone was like, “No, I don’t think we sent that for BTS.” But it turns out that it just happened that [Spreckley], his publisher had sent it and they wanted to roll with it, so it was a surprise for all of us. When the album went No. 1, we just went ‘What!’

Ray Michael Djan Jr. on “I’m Fine”: Obviously, [Foster and I] wrote [BTS' 2016 single] "Save Me" so once we realized it was a response to it we had an idea of what we wanted to say in the song. But it’s always a collaborative effort to work with their writers as well to make sure it translates into Korean perfectly and means something to the guys. We took a lot of influences from drum and bass, and the way some of those songs feel in terms of the energy in those records. And then it was important as well to make sure that even though it’s like a drum and bass-R&B piece, that in the melody particularly it feels pop. Cause that’s what I think is at the core of what those guys are about. They love to dabble with R&B and hip-hop and other things but it’s definitely got to feel pop. It was basically a blend of a lot of different sounds, melodically, to make sure that the guys had that kind of open moment. Especially on the chorus when it opens up and they sing, “I’m feeling just fine, fine, fine,” It was so important that that repetition happened in the chorus. It was key for us really.

We were always wondering if we could use "Save Me" again because we did it in 2016 but since then and now the guys have become so much bigger so I was always like, ‘Ah, man, I wish we could almost re-release that song’ cause it was a big song for them but it would really work now. So I was happy when I spoke to one of the team and they were like, “We’re thinking of doing something again with ‘Save Me.’"

Ali Tamposi & Roman Campolo on single ‘Idol’:

Tamposi: [Their rep] gave us a brief that she wanted the melodies to be a bit more intense [than Love Yourself: Tear track “Airplane Pt. 2”]. She sent over a bit of interesting references. For “Airplane Pt. 2” she did want the lane of [Camila Cabello's] “Havana” [which Tamposi co-wrote] and all that, something in that area, but for this one go as far left as you can.

Campolo: But it does have a melody similar to another song that Ali wrote [hums some of “Havana”]. When we heard that, it felt like a compliment directly to Ali.

Tamposi: We did some melodies, but they chopped it up [with work from other songwriters] so you’ll hear some in the second verse, a section in the chorus.

Campolo: The whole bridge, that’s the largest chunk in the song that’s all us.

Tamposi: That’s the cool thing about them, that they’re able to chop up parts of your melodies and strategically place them throughout a song. And that’s what I thought about. They don’t come back with you with a bunch of notes that they want you to change and try again, they just take the best parts of what you deliver.

Conor Maynard on “Answer: Love Myself”: For me, it was very, very random. A friend of mine, whose name is Ray [Michael Djan Jr.], he was a producer I worked quite heavily with on my first album. We work together, he and I, all the time, and we write together. He reached out, he got tracks on their previous album. He kind of built up a relationship with their team. I was in the studio one day and he was like, “Oh I got sent a new backing track by the BTS crew. Do you want to write over it?” I was like, “Yea.” This was right at the end of a session. I basically wrote the chorus of the song. It was just a backing track, there were no vocals on it. We did it in like 15 minutes since we knew the lyrics weren’t really going to be that important since they were going to be translated anyway, into what they wanted to say. So we made the melody and such. I forgot completely that we had even done it, and then a few weeks later he called me and he was like, “Oh yea, they wrote back. They really like it, and they want to use it.” Sometimes labels say, “Yea, we want to use it” and nothing ever really happens so I kind of forgot about it again. The next time I heard of it was when their fans found the album credit listing and they leaked it on Twitter or something. My name was on one of the songs. Fifteen minutes, just getting some ideas and sending it on to them. It’s amazing. I was like, “Wow, I should write all my songs for them now!”