The music world is mourning the loss of a quiet genius — someone whose impact was heard by millions, even if his name remained unknown to most.

For decades, his work helped shape the sound of one of the most legendary acts in pop history. Yet he remained humble, content to stay behind the mixing desk while the world sang along.

This week, the four members of a world-famous group — rarely heard from together in recent years — broke their silence to pay tribute to the man who helped define their sound. Their heartfelt messages describe someone irreplaceable, filled with joy, warmth, and creativity.

It is now confirmed that Michael B. Tretow, the longtime sound engineer for ABBA, has died at the age of 80.

Benny Andersson shared: “You meant more to us four in ABBA than anyone else… Our music lives on, it seems, and you are the one who made it timeless. You were the finest sound engineer the world has ever seen. I miss you. And I’ve saved all your coconuts!”

Björn Ulvaeus called him a “warm, generous person and a good friend,” adding: “His significance for ABBA cannot be overestimated.”

Tretow was the sonic mastermind behind tracks like Ring Ring, Waterloo, and Super Trouper, contributing to every ABBA album — except their 2021 reunion. He began working with the group in the early 1970s and remained their trusted studio partner throughout their golden era.

Fans have also flooded social media with tributes, many calling him “the fifth member of ABBA.” He is survived by his wife Malin Hertzman and son Rasmus Tretow.