Dolby Stereo 4 channels in 50 s

The version of Dolby Stereo that took hold in cinemas was the one in 4-channel configuration, the primitive version of Dolby Surround.
Right channel, left channel, central channel and a single back channel.
The first movie with the four-channel audio configuration was “A Star Is Born”, obviously not the one in which are starring Lady GaGa and Bradley Cooper but the second remake with Barbra Streisand in 1976.

Star Wars, released in US theaters in May 1977, was the most successful 4-channel Dolby Stereo movie and made this encoding a standard.