If you are a true music lover – not just someone who subscribes to a genre – then you have a great appreciation for songs. And Abba wrote some great songs that they performed just above the norm. This is the original earworm; it’s the thing that sneaks up and gets stuck in your head. That’s what appeals to people, even if they don’t really like the band or the genre. Even their B side is really, really eye-catching. They have been taken from us for so long; we didn’t have a chance to burn them. It’s like people want the Beatles to get back together.

Anne Sofie von Otter, mezzo-soprano who recorded ‘I Let the Music Speak’, an Abba cover album with Benny Andersson

When they did “Waterloo” at Eurovision Song Contest, I remember enjoying it and thinking they were fun, but I didn’t buy the records; I kind of followed the snobs who said they weren’t good, for some stupid reason. I rediscovered them when I went to work in Basel, Switzerland, for my first contract. There was a wonderful record store where I bought a tape of “The Visitors”, and I lay in my bed, feeling sorry for myself, listening to it on my Walkman.

The great thing is Benny Andersson’s musicality – his ability to write a melody, his ear for harmonies. He does not lose sight of the fact that there is an element of folk music, Nordic music, baroque music. He is a great composer; he knows how to use different voices by interweaving and building it. There is a great melancholy in everything he writes, and it hurts you in this wonderful, pleasant way. When I was recording with Elvis Costello, he just called Benny. He came to the studio, and I was completely struck by the star – almost crying with excitement, which happens quite rarely. I was extremely taken by the situation, because I adored it. I still love it, but maybe less dramatically than it did then.

Judy Craymer, “Mamma Mia! »Creator

I was working for lyricist Tim Rice as a production assistant, and the first project I worked on was with Bjorn Ulvaeus and Benny Andersson, writing “Chess”. Meeting Benny and Bjorn was an inspiration in itself. I wanted to know more about why they wrote these songs, what was behind these lyrics, what were the ingredients of these songs. It was fascination for me, because they had a very strong feminine consciousness – these were songs that women sang, but Benny had written them. Seeing them working in the studio, I could understand that it was not just pop songs; there was a wonderful mix of hooks and choruses and production, and they were also Swedish, so there was a kind of melancholy. They are very serious guys; it’s not really the guys who dress in white, with platform boots. It was very interesting for me.

I was fascinated by the explosion of oxygen you get – you come out of melancholy and always end up with a high. Bjorn’s lyrics had daily connections and common themes about people, friendship, broken romances, a child leaving home for school. That’s why I think the songs lasted a lot longer than they thought they would. When I kept harassing them in the 80s, they would say to me, “Oh, Abba is finished. We move forward. But you don’t have to love Abba to love “Mamma Mia!” there is a much younger audience that did not know Abba as pop stars or performers. They just know the music. You play this music to a child, and it’s almost calming.

I’ve known them for a long time now, and I think they’re still amazed that everyone loves “Dancing Queen” so much and wants to dance to it. It’s a big celebration that they have another album because I met them when they broke up, and it’s a wonderful circle of life that they got back together. There’s an Abba song called “The Way Old Friends Do”, and it’s kind of like that kind of closure.