beauty

Level of compression == beauty: Beauty is the related to the number of bits it takes a subjective observer $O$ in order to encode data $X$ at time $t$:

$$\text{beauty}(X,O(t))=-\text{\# bits to code}X$$

For example, if you don’t get a hidden message in a song, the song was not able to convey the full information to you, i.e. you won’t find it as beautiful as you would have if you got the message. Someone can explain the hidden message to you - but this requires extra bits of information, so is not as beautiful to you as if you got it yourself.

Interestingness is the first derivative of beauty