ABBA has shared a heartfelt tribute to their longtime sound engineer, Michael B. Tretow, following his passing at the age of 80.

A key figure in the Swedish music scene for decades, Tretow played a vital role in shaping ABBA’s iconic sound during their peak in the 1970s.

In light of his death, all four members of the legendary group have issued rare and emotional statements honoring his memory and contributions. The band took to Instagram and posted the tribute.

Bo Michael Tretow (August 20, 1944 – May 20, 2025) was a Swedish sound engineer, producer, musician, and composer, best known for his work with ABBA. Often called the “fifth member” of the band, he played a key role in creating their famous sound during their most successful years from 1970 to 1982.

Born in Norrköping, Sweden, Tretow showed an early interest in recording. As a teenager in the 1960s, he experimented with sound in his bedroom, using basic equipment to try out new ideas. His passion for music and technology led him to Metronome Studio in Stockholm, where he started working in 1967. There, he met Björn Ulvaeus and Benny Andersson, beginning a partnership that helped shape pop music history.

Tretow was known for his creative recording techniques, which helped form ABBA’s rich and layered sound. He used effects like tape delay and vocal doubling to give their songs a full, polished feel. His careful attention to detail and love for trying new things helped make ABBA’s music stand out around the world.

Outside of ABBA, Tretow worked on the musical Chess and collaborated with other Swedish artists, including Ted Gärdestad and Lena Andersson. He also made his own fun and quirky albums, such as Let’s Boogie (1976) and Hystereo Hi-lites (1989), showing his playful side and wide range of skills.

In 2001, Tretow suffered a stroke, which led him to slowly step back from music.

According to the Daily Mail, Tretow is survived by his son Rasmus Tretow and his wife Malin Hertzman.