The art and craft of skillfully breaking silences with something worth listening to. Not to be confused with noise.
Man is a rhythmic animal - heart beat, speaking and walking paces play a large part in everyday life whether conciously or not. Man's hearing is evolved to hear prey and predators and sounds of the natural world. These sound receptors are naturally wired deep into the brain as quite ancient devices and provoke a pronounced effect both mental and physical. Music, although artificial, has the power to provoke the same deep and powerful responses by the same means.
Music is a stream of Notes of varying Pitch, played at a particular Tempo to a particular Rhythm forming a melody or tune. It may or may not have Harmony. There is also a concept called Tone Colour which is the quality of the sound (Clarinet versus comb and paper)
Music is a performing art with cultural and social aspects. Music is regional and ethnic. It is a defining aspect of a culture and is used in its major celebratory moments.