By definition, all commercial records pressed before the
introduction of stereo LP records in 1957 were monaural (mono),
which means they were only able to output one signal channel to
speakers or headphones. The driving force behind these two-
channel “stereophonic” LPs—a concept that had been tinkered with
since the 1930s—was the idea that recorded music sounds better
when each ear is presented with a different element of the
overall sound. In the early ’60s, only adults with deep pockets
could afford a state-of-the-art “hi-fi” stereo system with two
speakers. The biggest consumers of pop music, kids and
teenagers, made do with cheap mono record players with only one
speaker. Stereo records also cost a dollar more than mono discs.
For these reasons, artists that appealed to adults, like Frank
Sinatra, were more likely to put out stereo recordings than pop
stars. That all began to change, though, in 1966, when
inexpensive stylus cartridges allowed stereo records to be
played on mono turntables. Most of the po