Music lacks the specific sound-concept association that is characteristic of speech, making exchange of information less precise. Nevertheless, verbal language has not replaced musical communication. Music is common to all peoples and cultures, probably because certain impressions and emotions are communicated more successfully by direct musical intuition. Different musical traditions have common features which can be explained by acoustic, auditory and neurobiological mechanisms. Harmonic (consonant) intervals--octave, fifth, fourth, third--play an important role, and are also spontaneously preferred by animals (rats). Pitch and chords are simultaneous patterns that are normally controlled by the right (non-speech) hemisphere of the brain. Rhythm, speech and language, and prosody are sequential patterns that are controlled by the left hemisphere. Musical sounds are stored as structural memory patterns, analogous to poetry or rhyme, independent of comprehension. Simultaneous singing and rhythmic movement facilitate initiation and fluency of speech. Musical functions are included in neuropsychological test batteries. In medicine, music is used as an alternative channel of communication in aphasia and developmental disorders, and in psychotherapy.