It is known that in unwritten traditional music, both in unison singing and in performances by two or more instruments, there occur little rhythmic maladjustments and even variations of intonation and changes of notes, apart from the natural changes of register. When these variations are very marked, they produce a real heterophony. But the intention is the only thing to be kept in mind: the intention to form one single sonorous block. Therefore, there is a great difference between a defective adjustment and polyphony or heterophony properly so-called. Heterophony is the singing or the simultaneous performance of several voices or instruments which do not observe musical order, and which enter the ensemble when they wish, without paying attention to order. Heterophony appears to be a particular manifestation, among Indian people and perhaps also among people who are already incorporated into our civilization.