fastbreeder is an experimental genetic programming synthesiser.
Fastbreeder is essentially a 4 button synth. The idea is to grow code by choosing from a range of automatically generated variations of functions, you don't have to know how they work, but each function creates a sound which can be selected by you.
The following generation is then created containing mutants of your chosen sound. You can refine and develop the sound just by auditioning and choosing the best one each time.
The interface shows you the code graphically, as a tree. These trees are attempts to clearly represent code structure, giving you some feedback on what is being evolved. Conventional listings are not that informative with GP (genetic programming), as deeply functional code such as this is hard to read linearly (see below).