Fun music gear history: The 1949 format war
The late 40s was a transformative time in music technology. While magnetic tape technology was being spirited from the Nazis back to the US (setting the stage for multi-track recording), a couple of American music companies were in a fight to the death over the future of records.
In June 1948, Columbia unveiled the 12-inch album that spun at 33 1/3. The following March, RCA countered with the 7-inch 45 RPM single. This format war shaped the future of how we consumed music for decades
Check out this doc on the subject.

