As there are only really two forces acting in the universe beyond the confines of the atom, those being the electromagnetic force and the kinetic energy created by Time, it stands to reason that all things can by and large be boiled down to an interaction between these two forces, and this includes music. So when a string is struck, bowed or plucked, the interplay between the object operating upon the string, the string itself, and the air and other components within the environment, combined with the kinetic energy provided by Time which enables the action to occur in the first place, all combine to provide a musical sound.
As with black body radiation, it is most likely the excited vibrational frequencies of the electrons within the atoms of which the string is composed which determine the nature and frequency of the sound.
This explanation would also account for the sound of the wind as air molecules crash against each other whilst interacting with the environment.
So when I play the piano, I am using both the kinetic energy of Time and the electromagnetic energy of electrons to create a, hopefully, harmonious sound.
New Age Physics 