Berlyne and aesthetics

Berlyne uses the notion of arousal as a way of understanding the nature of aesthetic appreciation.
Here arousal denotes the motivational level of emotions - emotions are aroused when they undergo a higher than usual level of activation.
Extremely high levels of arousal are unpleasant, and so as the arousal level approaches the upper extremes, return to a lower level of arousal is pleasant.
The arousal level is determined in part by the amount of information transmitted, which in turn depends in part on the subject. Some information may already be known, and some may fit into a more general matrix from which interrelationships (hence familiarity) can be derived.
Thus for an uneducated subject, the stimulus may contain so much information that it produces an uncomfortably high level of arousal and so is unpleasant.
On the other hand, a stimulus which is thoroughly familiar to the subject may result in a low level of arousal because it carries very little information.
To tie this into the common sentiment that one person's music is another person's racket, consider the kinds of music with which you are most familiar.
If your musical experiences are based on Pink Floyd or Tori Amos, then the Fifth Brandenburg Concerto will be so unfamiliar as to produce an unpleasant level of arousal.
If you have listened to mostly Bach and Mozart, then Cornflake Girl will produce an unpleasant level of arousal.
On the other hand, too much familiarity is not good: if you listen to Beethoven's Ninth Symphony forty times in succession, the forty-first time you hear the piece it will produce a very low level of arousal.
Of course, the information content alone is not the only contributing factor.
For example, according to McClelland's theory of affect, any stimulus is compared with the subject's present adaptation level - a measure of the types of stimulation which the subject has been receiving or is expecting to receive.
Small departures in either direction from the subject's adaptation level produce a positive affect, while larger departures produce a negative affect.
In this way, affect measures the level of novelty of a stimulus.

So familiarity and novelty are necessary together in order to attain a pleasurable level of arousal.