Tone

Aleatoricism is the creation of art by chance, exploiting the principle of randomness. The word derives from the Latin word alea, the rolling of dice. It should not be confused with improvisation.

Eg: Dice Man, Music with built in choices, all Movie decisions made by flipping coins etc,  An example of aleatory writing is the automatic writing of the French Surrealists involving dreams, et cetera

see wikipedia for more info:

http://en.wikipedia.org/wiki/Aleatory