Analog Recording
Sound can be recorded with electrical equipment.
Above we presented that sound, such as spoken word or an instrument, is made up of variable, continuous air pressure waves. Analog recording and reproduction of sound uses electrical voltage controlled devices (circuit boards) to record and process those variable air pressure waves as continuous electrical pulses of various voltage levels (an analog signal). The higher the amplitude of the sound, the higher the voltage level. Electrical circuits are designed to process this continually changing electric voltage signal.
The analog recording is an almost complete and continuous electrical reproduction of the various changes in air pressure created by the original real life sound and the resulting waveform (”analogous” to the physical wave form). The analog electrical pulses from the microphone and into a mixer (circuit board) or directly to the recorder and can then be converted to magnetic charges when saved on tape. The tape has a metallic (ferromagnetic) coating (ferric/iron oxide, chromium dioxide, cobalt), which particles are magnetized (almost indefinitely until erased or recorded over) by a electromagnetic coil in the head of the recorder as the tape passes over.