The news of Abbas' reunification was, of course, world news.
To prevent the spread of rumors before the launch, the studio musicians were asked not to reveal anything about the project.
When the Stockholm concert orchestra, with about 30 musicians, came to the studio on Skeppsholmen in Stockholm two years ago, Benny Andersson began with a short speech.
- Benny said "no social media".
So there were no phones or pictures.
Or ... pictures were snapped but they were not uploaded until last night.
I think the whole network was flooded with images from the recording, says Johan Ahlin.
Was it hard to keep it a secret?
- It was quite difficult actually.
We are a lot of musicians so it's cool that it did not leak out.
But there is a code of honor that you follow of course.
Then the mother-in-law asked afterwards: "why did you not tell?"
"Became sharp mode"
At first, the orchestra musicians were not quite sure that it was actually Abba who wanted to hire them.
- Benny's organizer Göran Arnberg got in touch three, four years ago and put out a hook.
Then we did not understand that it was Abba it was about.
But two years ago, the situation suddenly became sharp.
The orchestra was called in, listened to drafts of the new songs and was able to start recording.
- The girls had added a little song that sounded very nice.
When I then saw the titles, I understood that they were Abba songs.
I have played the musicals Chess and Kristina from Duvemåla before and recognized Benny Andersson's tonal language.
He has his own golden ratio.
Johan Ahlin has previously put French horns on songs for several big stars, including Céline Dion.
But the Abba job is booming.
- It's music history, like being part of the premiere of a Beethoven symphony in the 19th century.