"Four-track and 8-track cartridges coexisted on the marketplace for some time, with the 8-track format eventually defeating by attrition its look-alike cousin (before in turn being overtaken by the cassette format). Although extremely similar in appearance (the only obvious difference between the two being a large hole in the top left underside of 4-tracks), the two formats were not at all compatible, having been developed and marketed by two different and competing factions. The 4-track system was refined and marketed as a car accessory by Madman Ernie Muntz, a west-coast used car dealer looking for something he could offer as an accessory to boost his used car sales. His marketing and distribution arrangements were spotty at best, relegating the 4-track format to the inferior (when compared to 8-track) status of a regional phenomenon, most popular in such locales as California (Muntz's home base) and Florida, but unpopular or unknown in many other areas."
"The 8-track format, on the other hand, was developed by a diverse consortium that included the Ampex Magnetic Tape Company, Lear Jet Company and RCA Records, and enjoyed the tremendous advantage of being championed at its inception by Ford Motors, which in 1965 (debuted September 15) offered 8-track players as an option in their complete line of 1966 model cars. At first, 4-track and 8-track tape players were just car accessories. Home players were not introduced for another year or so. Accordingly, both 4-track and 8-track prerecorded tape cartridges were originally sold only in such outlets as auto parts stores and roadside truck stops."
"The 4-track cartridge format had had a head start over 8-tracks. Originally developed in 1956 (also in conjunction with Ford Motors), the 4-track format was originally forsaken as unmarketable, and lay dormant until the early '60s, when enterprising Ernie Muntz saw its potential. He acquired rights to the format and began marketing both hardware (players) and software (prerecorded tapes), licensing music from major record labels. It was perhaps Ernie Muntz's initiative that rekindled Ford's interest in offering an in-dash tape cartridge system. The development of the 8-track format took the basic 4-track technology and refined it, making changes designed to make the tape less likely to jam while playing, and to increase accessibility to individual selections on the tape."