The eight-track cartridge tape system was devised by William Powell Lear, the founder of the LearJet corporation, in the 1960s. Lear's invention is similar to its predecessor, the four-track tape. The main difference is that the eight-track tape is divided into eight channels, or tracks, where the four-track is divided into only four. Doubling the number of tracks doubled the amount of playing time on the tape, from about 40 minutes to about one hour and 20 minutes. The narrower channels of the eight-track tape, however, sometimes resulted in one track "bleeding" into another so that strains of one track could be heard over another. The eight-track tape was a popular audio format from the mid-1960s through the early 1980s, when their popularity finally almost completely gave way to audiocasette tapes and vinyl Lp records.