Milk and Cereal

This morning I realized I am almost out of Cheerios, after I had just bought a couple of cartons of soy milk (which is really soy juice but whatever). So within the next day or so it's off to the store (again) to get more cereal. Inevitably, because I don't care to gauge how many cups of cereal line up with the amount of milk I have...I will have to go to the store and buy more milk because I have extra cereal on hand. This got me to thinking about those two industries and their co-dependence. I don't know for sure, but you'd think that the cereal industry would invest mightily in the milk industry and vice versa. Different products entirely, but most people these days don't consume one without the other. The health of the milk industry is forever intertwined with the health of the cereal makers, and since we don't buy them in equitable amounts, the endless cycle of "out of milk need cereal / out of cereal need milk" continues. What is the milk to the music business' cereal? What do musicians invest in to ensure a forever? Or maybe music is one of those rare cereals that just tastes good on its own. Thoughts?