Crying babies calm down at the simple musical tones of their mother's song. Before science can deal with these ultimate questions in music perception, it must first consider many more basic problems. Great physicists like George Ohm and Hermann von Helmholtz began studying these basic questions over 150 years ago. The results are fascinating but hard to describe. In a nutshell, it is increasingly clear that musical tone perception is a pattern recognition process, even for the simplest sound attributes like pitch and timbre.
Vision provides an analogy.
In the auditory system, incoming sound waves are mechanically converted into resonant oscillations of the basilar membrane, the sensory organ in the inner ear. The brain recognizes a particular vibration pattern as pertaining to a given musical tone, much as it recognized a particular visually perceived geometrical pattern as a given letter. Recent advances in research on the perception of musical tones have led to new theories in musicology to explain tonal consonance and dissonance, harmony, tonal dominance, the sense of tonal return, and many practical aspects ranging from instrument performance techniques to music hall acoustics. Even these advances leave us far from answering the ultimate questions about the effects music has on people. These pertain to the more complex higher functions of the brain.