During the first half of the 1920s, engineers at Western Electric, as well as independent inventors such as Orlando Marsh, developed technology for capturing sound with a microphone, amplifying it with vacuum tubes, then using the amplified signal to drive an electromagnetic recording head. Western Electric's innovations resulted in a greatly expanded and more even frequency response, creating a dramatically fuller, clearer and more natural-sounding recording. Distant or less strong sounds that were impossible to record by the old methods could now be captured. Volume was now limited only by the groove spacing on the record and the limitations of the intended playback device. Victor and Columbia licensed the new electrical system from Western Electric and began issuing electrically recorded discs in 1925. The first classical recording was of Chopin impromptus and Schubert's Litanei by Alfred Cortot for Victor.

What was an early took used to amplify sounds?