Form: always surprised

There's a pumpkin plant in our (tiny) garden that's stretched and arched around the back terrace, coming into bloom here and there, but now, suddenly, four metres away from the roots, an orange fruit has finally taken hold, a future jack'o'lantern suspended between an old rose and the garden shed. Why there? Why now? How does it manage to arrest attentions, surprising every passer-by?

I've tried several times to write something useful about musical form. I've thought about the origins in song and dance, and the license gained by the invention of absolute genres. I've considered the uses and benefits of calculation (or the failures of miscalculation). But in the end, musical form is about finding the right mix of materials and time, playing those elements against human memory and expectation, and then -- if you want to make music that does more than function -- you grab something surprising and incalculable, you add that pumpkin four metres down the vine.