 Six of the remaining seven tracks were then used to individually record the vocals of each member of The Beach Boys, and the eighth track was reserved for any final 'sweetening' overdubs of instruments or voices.3M introduced the 1-inch eight-track version of their model M-23 recorder in 1966, probably the first mass-produced machine of this format.It remained in production until 1970 and was used by many top studios worldwide including Abbey Road Studios in London.