Pictures and sounds alike are made with numbers. Sometimes, I start with a pattern of numbers "out there" somewhere. Those numbers might be come from a musical passage represented in MIDI format, or from a bitmap in represented in PCX format. At other times, I manufacture the numbers for my sights and my sounds directly from numbers I generate myself.
Both getting the numbers in the first place and then putting them back in the last place are two of the crucial steps in the overall process. But Image Algebra is what happens in between.