Critters for Mac

From grain-brain:

Our goal at grain-brain is to provide a versatile, easy-to-use tool that anyone can use to compose original music. No musical ability required. Listen to a batch of critters, rate them and create a new generation based on your preferences. Breed them repeatedly, 'steering' your critters towards your desired destination. Or, start over with a fresh litter of random critters. Critters is not a loop-based composer. There are an infinite number of potential compositions (Well actually only 2 to the 10,000th). Create endless subtle (or not) mutations of your favorite critters. If you know what you like you can compose.