StatBalStream | SuperCollider 3.13.0 Help

Charles Ames' statistical feedback is a type of weighted random number generator that is useful for generating streams of random numbers that sound more "natural" and "balanced." Statistical balance keeps track of the distributions of its own output and compensates for short-term lack of diversity. A "heterogeneity" parameter allows you to control how strong this compensation is -- low heterogeneity approaches deterministic behavior (like serialism) and high heterogeneity behaves more randomly.

The pseudocode is as follows:

Let W be a list of n nonzero weights.
Let h be a nonnegative heterogeneity scalar parameter.
Let a be an accent scalar parameter (scalar).
Set S to an array of n zeros.
To generate a new output of the stream:
- Find the weight k so that S[i] + (a + h * rand()) / W[i] is minimized, where rand() generates a random number from 0 to 1 for each index.
- Add a / W[k] to S[k].
- Return k.

W, h, and a can all be changed during the generator's evolution.

References (all Ames, Charles):

"Statistics and Compositional Balance" Perspectives of New Music 1989
"A Catalogue of Sequence Generators" Leonardo Music Journal 1992
"Quantifying Musical Merit" Interface: Journal of New Music Research 1992

Class Methods

.new

Arguments:

states	An array of the states to return
weights	An array of weightings, one for each state. Weights may be zero.
heterogeneity	any positive float. Whilst weightings will be approached in the long term, how quickly this occurs relative to serialism and the tolerance within which a running histogram of results fluctuates depends on the ratio of heterogeneity to accent (by default 1). Heterogeneity 0.0 gives fully deterministic results, like serialism. Increasing heterogeneity increases the shuffling of order of appearance of states, that is, less predictability in the short term. If heterogenity is really large then floating point problems will eventually occur.
length	Number of calls to next before returning nil for sequence end. Default is inf for forever.