Why were vinyl record albums 33 1/3 RPM? Because AT&T invented them that way. The technologies that eventually led to the microgroove "lp" were pioneered by AT&T as a way to fit prerecorded radio programs onto a single disk. AT&T engineers slowed the recording and playback speed from 78 to 33 1/3 RPM and substituted vertical groove cutting for the old, wider, side-to-side method. The result was a 16-inch-wide record that could store 23 minutes of music on each side -- or an entire half-hour radio show, minus the commercials. And the record had better stylus tracking, lower harmonic distortion, and a wider frequency response.