I googled your question up with this list. The first said it was easy, but time consuming. I didn't read any of the other links. I am posting the link in case you don't get any answers.

Here is a link that might be useful: cleaning cedar siding

Let weather take care of it.

Thanks! Your suggestion of letting the weather take care of it is excellent, if it were on a wall exposed to weather.

The area with mud is recessed back of the entry way where weather never touches it (very high up).

Other suggestions? Other than climbing a ladder to scrub manually and break my neck in the process!

I'm not sure I'm picturing it correctly, but if it's very high up in a recessed entryway and weather can't get to it, is it really noticeable? Sounds like a person would have to deliberately look up there to see it. So maybe it's the just knowing it's there that is bothering you?

Only other thing I can think of is, if a power washer didn't blast it out, I'm not sure what can, so maybe hang some nice decorative thing to hide it?