Processing auditory complexity

A sequence of events produced according to certain probabilities is a "stochastic process," and a stochastic process in which probabilities  are dependent on previous events is a "Markoff process." If music is a Markoff process, uncertainty, information, and meaning will gradually decrease as probability increases. "Systemic uncertainty" inevitably occurs at the beginning of a composition when the norms and probabilities of the piece are being assimilated. When these norms and probabilities have been established, the composer may introduce "designed uncertainty" to combat the tedium of the expected. Designed uncertainty, then, will decrease probability and increase the amount of information provided.

…………

Redundancy is important in music in that it allows a listener's internalized probability system to take over so that he or she may pause to evaluate what has taken place and will take place in a difficult composition. Because of the high level of redundancy in music, we are able to understand incomplete musical events so long as what is omitted is statistically probable. Redundancy also combats noise, whether acoustical (which comes from poor building acoustics, transmission systems, or extramusical sounds) or "cultural" (resulting from the disparities between the habitual responses a piece requires and those actually possessed by a listener).

Renée Cox Lorraine, Music: Tendencies and Inhibitions