Quadraphonic 8-Track (also know as Quad-8 or Q8) was a discrete 4-channel magnetic tape cartridge system introduced by RCA Records in 1970.
It was based on the 8-Track cartridge, and cartridges were almost identical except for a small sensing notch in the upper left corner of the cartridge. This signalled a quadraphonic 8-Track player to combine the odd tracks as audio channels for the first program, and the even tracks as channels for the second program. The format was not fully compatible with stereo or mono 8-Track players – although quadraphonic players would play stereo 8-tracks, playing quadraphonic tapes on stereo players results in hearing only half the channels at a time.
Q8 cartridges had two ‘sides’ whereas 8-Tracks has four sides or programmes. To compensate for the reduction in programmes due to the doubling of tracks, Q8s used thinner tape to try and increase playing time.
Around 200 different Q8 titles were available in mid 1972. Blank media was also available for home recording.
The last release in the quadraphonic 8-track format was in 1978, although most had stopped appearing by the end of 1976.