What Media Playback Button’s Symbol Is Derived From Musical Notation?
In musical meter and poetry, a caesura is a complete pause in the composition or line, respectively. Caesuras are noted on Western sheet music with two vertical slashes, similar to, but significantly thicker than, the forward slashes found in the beginning of web site URLs.
This particular parallel notation found life off the page with the advent of media remotes and control interfaces. Designers, searching for an intuitive way to indicate the music would be paused when the button in question was pushed, labeled it with a slightly modified version of the musical notation for pause itself, the caesura.
Image courtesy of Aconcagua.