An information transmission system is broken down into a sound recorder, a transmission medium and a sound reproducer; a digital audio signal is produced from MIDI music data words through any kind of modulation technique such as, for example, Y-modulation technique, P-modulation technique or Q-modulation technique, and the digital audio signal is transferred from the sound recorder through the transmission medium such as a magneto-optic disc, a wire communication network or the free space to the sound reproducer, when the digital audio signal reaches the sound reproducer, the sound reproducer analyzes the digital audio signal to see what modulation technique was employed to produce it, and demodulates the digital audio signal through an appropriate demodulation technique, thereby permitting user to employ any sound recorder to produce the digital audio signal.