 At first, in the early 1930s, the blanks varied in both size and composition, but most often they were simply bare aluminum and the groove was indented rather than cut.Typically, these very early recordings were not made by the network or radio station, but by a private recording service contracted by the broadcast sponsor or one of the performers.The bare aluminum discs were typically 10 or 12 inches in diameter and recorded at the then-standard speed of 78 rpm, which meant that several disc sides were required to accommodate even a 15-minute program.