Bird song is considered as a primitive form of music, and as an evolutionary anticipation of human music. Evidence is seen in the use of elementary musical devices: in the avoidance of mechanical regularity (principle of the "monotony threshold"): in the learning of songs and tunes : in the partial detachment from utility, and the playful cultivation of sound production : and, finally, in the tendency of species with more elaborate and, by our criteria, more "musical" songs to spend a larger fraction of the minute, day, and year singing (the "correlation of quantity with quality"). The best singers are those with more variety and complexity in the use of elementary musical devices.