Your typical CD can hold around 70 minutes of music, yet many albums are only around 45 minutes long. Why, in this digital age, aren’t the songs longer, or the albums don’t have more of them? Call it a legacy of records past: when the first phonographs came to the market, the size of the stylus that went into the grooves to produce sound dictated the number of the grooves that could fit on the machine, and the number of grooves determined the length of the song. As it happened, for several decades the length of a song that could fit on one side of a 78 rpm record – the standard of the earliest players – was between three and four minutes. And then the LP came along.

On this day, June 18, in 1949 Columbia Records unveiled its now “Long-Play” record, the 33 1/3 (for the number of rpm.) The standard for the next thirty or so years, the LP could hold around 23 minutes of music on each side.

The LP was soon challenged by RCA’s new record format, the 45 rpm “EP” (Extended Play.) The 45 became the popular choice for singles, able to hold five minutes of song on each side, and their smaller size made them perfect the replace the 78s in jukeboxes. Thinner, smaller 45s could fit 100-200 at a time in jukeboxes, compared to only one-tenth as many for 78s.