The vinyl record that was introduced in the early 1950s to replace the shorter-play records previously used. Rather than their 78 rpm rotational velocity, the LP rotated at 33 1/3 rpm and used narrower grooves. Accordingly, it gave a playing time of between 15 and 30 minutes per side, depending on the how heavily the signal was modulated, the amount and character of its bass content and the amount of material available.