…creates two separate instances of my_integrate. Each output gets an independent instance. That was not obvious to me from the code, since it looks like two calls to the same function. The way it is written, I would have expected "prev" in a single instance of my_integrate to increase by in1 + in2 for each audio frame (one frame being 1/SampleRate).
I like the behavior that it actually implements, I just want to point it out in case it is confusing to anyone else.