To transmit/receive information without disturbing the listening of sound.

A modulation apparatus generates a sound signal of a waveform obtained by combining a plurality of frequency components. When superimposing information on the sound signal, the modulation apparatus modifies elements (frequency values or levels) of frequency components in accordance with the information. The mode of modifying elements is described in a parameter stored beforehand, and the modulation apparatus selects one of a plurality of parameters in accordance with the information. For example, when superimposing information in a case where there is a waveform represented by combining frequencies f0, f1, f2 and f3, on the basis of the parameter describing a shift amount, the modulation apparatus shifts the frequency f1 just by 1, shifts the frequency f2 just by 2 and shifts the frequency f3 just by 3. Namely, when a case (a) where no shift is performed is defined as a reference, the modulation apparatus combines (b) waveforms of frequency components obtained by shifting the frequencies from a reference value just by values corresponding to the information.