Okay, I’m not actually sure about that, but Golden Earring started releasing music in 1965 and I think he’s the first person to ever record as a full band member to die. I only know their two big hits and didn’t know the band members’ names, but I remembered people calling them out as one of the oldest band to still have all their members living, so I looked them up just now. A few of the early members don’t have Wikipedia pages, but based on Google searches I don’t think anyone else has died. Wikipedia lists someone who only appeared as a harmonica player in 1979 as a “band member” and he’s dead, but the page for the album he plays on lists him as an “additional musician.”

Quickly looking at online discussions about this, I don’t see who beats them, or who would beat Sabbath if Ozzy had hung on another week.

I’m counting the beginning of a band by when they start releasing music. I know that’s not the real beginning, but I don’t worry about early members if they didn’t record, so I think it makes sense to start counting when they start releasing music.