An instrument for the mechanical registration and
   reproduction of audible sounds, as articulate speech, etc. It consists
   of a rotating cylinder or disk covered with some material easily
   indented, as tinfoil, wax, paraffin, etc., above which is a thin plate
   carrying a stylus. As the plate vibrates under the influence of a
   sound, the stylus makes minute indentations or undulations in the soft
   material, and these, when the cylinder or disk is again turned, set the
   plate in vibration, and reproduce the sound.