The ex-group's frontman Robyn Hitchcock confirmed the news of Seligman's death on Friday on Facebook.
"I'm writing this as Matthew Seligman slips out of this life and into wherever souls go next. Everybody goes, but none of us were expecting Matthew to leave us so abruptly, forever," Hitchcock said.
His friend and former bandmate Thomas Dolby shared on Facebook that Seligman "suffered a catastrophic haemorrhagic stroke" after recently being admitted to St George's Hospital in London for COVID-19.
"I am so sad to have to bear this terrible news. I have loved him as a friend and a fellow musician for 40 years," Dolby wrote.
According to Billboard, Seligman joined The Soft Boys in the late 1970s and was part of played on the psychedelic band's "A Can of Bees" (1979) and "Underwater Moonlight" (1980) albums.
He later played on solo albums by Hitchcock and Dolby.
Seligman's impressive discography also included playing alongside David Bowie, The Waterboys, Thompson Twins, Morrissey, Chrissie Hynde, Sinead O'Connor and Tori Amos.
The musician is survived by his partner, Mami; and his children, Daisy and Lily. RDSRDS