Recording generally starts with sound waves that are analog in nature. A microphone converts the vibrations in the air into an analog electrical signal; the amplitude of the electrical signal matches the sound amplitude. Vinyl and tape are analog recordings of the sound; the amplitude of the groove vibrations or the amplitude of the magnetic fields in the tape vary the same way as those of the sound source. For digital recordings the analog signal from the microphone is converted to a binary digital signal which is recorded as ones and zeroes on a CD, DVD or disk drive. Electronic instruments create digital signals directly (MIDI) which can be recorded or manipulated with a computer. Digital signals are converted into analog signals, amplified and then sent to a speaker to convert them from electrical analog signals to sound vibrations. Here is a schematic of electronic recording and transmission.