His Dutch father and his Russian Romani mother had met in a concentration camp during World War II.

[1] The Outsiders reached a measure of success, opening up for The Rolling Stones in 1966 and scoring a number of hits in the Netherlands.

[4] Leading what Billboard called "the leading Dutch beat group," Tax had a high-profile—he was reported to have the longest hair in the country,[5] and lived a lavish lifestyle involving expensive dinners, chauffeur-driven cars, and friendships with Little Richard and Johnny Hallyday, as well as rumors of an affair with Brigitte Bardot.

[6] Although The Outsiders' records were not distributed in the United States, Tax did go overseas and made friends with notable musicians such as Tim Hardin, Richie Havens, and Crosby, Stills, Nash & Young, and attended the Woodstock Festival.

[3] In 1974, he won the Silver Harp, an award for musical talent and had significant success with a couple of solo singles, "Miss Wonderful" and "It ain't no use".

[8] After his playing career had ended, he concerned himself mainly with songwriting and wrote a number of hits for Dutch artists such as Lee Towers ("It's Raining in my Heart")[9] and Champagne ("Valentino", "Oh Me Oh My Goodbye", and "Rock 'n Roll Star", the latter charting at #2 in the Netherlands and #83 in the United States).

[13] His biography, Wally Tax – Leven en Lijden van een Outsider, was written by Rutger Vahl and came out ten years after his death in 2015.