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[maplecleff1215]

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[ted]

....I've really just been mashing keys until I found something that sounds good....

That is pretty much all I have ever done. A set of rules cannot decide what sounds good to an individual player. Store all the "good" sounds in your memory, build them up over the years, and constantly look for new ones. I am not familiar with Alfred, and am a rather peculiar improviser at the best of times, so I shall leave it to other people to give you specifics. Only you yourself can decide what sounds good though, that much I am very sure of.