The 78 rpm disc, the recorded music standard since the 1920s, is soon to be phased out...perhaps by 1958. The "33 & a third" LP and "45" single, first marketed in the late 1940s, have become THE music format of 1950s America. These are single-channel monophonic mediums. 2 years ago, 2-channel stereophonic reel-to-reel tapes were introduced (for nearly three times the price of a 45 or 33 1/3 rpm "album"). It is believed that stereo LP records will be on the market by 1958.