Here are multiple overlapping horizontal waves with slightly different frequency, amplitude, and phase. (Meaning they do not neatly line up.)
My code had a bug, and I spend way too much time hunting it down. In the process I generated many images trying to isolate the problem.
Actually there were two problems. One was an actual bug, the other probably should be called a prototype. I had an idea of what I wanted, wrote some code that I thought might work, but I was not sure. So I tried it to see what would happen. The result was close to, but not quite what I intended.