I think that question would vary significantly from one culture to another. For example, music in western cultures is based on a different scale (is that the correct word) than music in the far east. People from one culture might realize that they are hearing the music from another culture, but they probably would not be quick to recognize the patterns, and it would certainly not be part of their learned heritage.

On the other hand, maybe music could be universally defined as sounds (usually with some pattern, i.e., tempo, pitch, volume, etc.) that are pleasing to at least some people and which, for whatever reason, have some meaning to those people. The sounds might be simply soothing, they might be meaningful to them in some way. Some sounds remind us of people, places, events, or feelings, and they can, in turn, evoke feelings within us, even if at an unconscious level; the reaction of individuals to a particular piece of music will vary in the same way and for the same reasons that apply to all symbolism. Hearing music can even affect physical actions; people move mover quickly when they hear music with a quick tempo than when they hear slower paced music. Slow soothing music is often played in stores to get customers to linger.

Or maybe music is simply whatever a person says it is for him!