Among musical instruments one type is of universal distribution: the percussion instruments, or perhaps better instruments for producing noises that carry the rhythm of the song. In the simplest cases these are sticks with which boards or other resounding objects are struck. But besides these we find everywhere the use of some kind of a drum: wooden, hollow boxes, hollow cylinders or hoops covered with a drum head of skin. Rattles, and locally other devices for producing noises occur. Not so general, for musical purposes, is the use of wind instruments. Whistles used as calls are perhaps universal, but the flute or pipe is not used everywhere as a musical instrument. Still more restricted is the use of stringed instruments. At the time of the discovery they were entirely unknown in America. Among primitive tribes, including the whole of America, song was accompanied only by rhythmic beating on instruments of percussion. It is interesting to note that the beats did not always coincide with the accent of the song, but had often an independent, though coordinated rhythm (see p. 315). Singing in several parts is also unknown in primitive music. In Africa solo singing and response of a chorus occurs, and a kind of polyphony due to the overlapping of these. Sometimes true singing in parts has been observed in Africa. Music is always expressionistic and we are apt to associate with a tune and rhythm a definite mood, but these associations vary considerably with local styles. I have referred, in another place, to the feelings associated among ourselves with the major and minor keys. These are not by any means shared by people who have grown up under the influence of another musical style. It is likely that the symbolic meaning of music alone is vaguer than that of song; but it is difficult to reach a definite decision in regard to this question, for there is very little music without song or without association with symbolic or representative actions. The condition is perhaps comparable to that found in the symbolic significance of graphic and plastic arts, the connotations of which are, as we have seen, certain only when a definite relation between form and implied content exist. It is intelligible that a type of tune that is always applied in mourning ceremonies will produce the proper emotional effect, while the same type of tune without such definite setting might have quite a different effect.