Making it sound interesting

This week I've been struggling with creating an interesting piece for organ duet. I find that it's difficult to control the texture when writing for four hands and four feet. When you make an interesting texture, it's possible to lose yourself in it and forget the flow of time, forget how the listeners would perceive it in motion.

For example, at first, I created a piece with one eighth note motion flow. It seemed interesting enough. But it went for 5 and a half minutes. The rule about keeping interest going is to change something before it gets boring. Usually it's less than 2 minutes.

It's like scenes in movies. One scene usually lasts about 1 minute, sometimes up to 2 minutes. Of course, there are slow movies with long scenes but they are a separate breed.
So I today thought about inserting a middle section in the piece. This had to add contrast. How about a smaller note values? Maybe 16th notes.

And sure enough now my piece has 3 sections, like in ABA form - eighth-notes, 16th notes and eighth notes again.

It doesn't mean this piece will be interesting when I finish it though. It just means I eliminated just one problem.
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Quite a few more to go.