Best guess based on your information is Cooper's hawk.

That's what I always thought I saw in the neighborhood. But comparing this to the book I have, it's chest seems to lack the color they show. Could it be an immature?

Deb in PA

Could be. Here's what the breast of an immature Cooper's Hawk looks like. Only thing is, they're brown above, not light gray:

{{!gwi}}

The two-tone call you describe is atypical for a Cooper's Hawk, too -- their call is usually a series of one-note harsh keks. But if it was an immature, possibly they make a different call -- especially if they're frustrated while hunting for food.

Behavior sounds more like it was hunting. It probably had seen something yummy-looking lurking in the tree and was trying to get at it.

I wonder if you could have seen a Goshawk? The males are a few inches larger than crows, but length can be difficult to estimate. If there's a forest anywhere near you, it's a possibility -- they do breed in the NE corner of PA and winter in all of PA. Their display call is described by Sibley as a "wailing gull-like KREE-ah, repeated regularly. Juvenile begging call a plaintive scream kree-ah." I'm not sure that the recording I've linked below is that call, but there it is for what it's worth. Call at nest is described as a loud, cackling kye, kye, kye, which is what this recording may have captured. From the underside their tail looks rather as you've described it, and they do fly with their tails closed as well as open. When flying with tail closed, the shape is similar to a Cooper's Hawk -- the wings are a bit longer and thinner.

{{!gwi}}>

You can go to the Cornell site at http://www.birds.cornell.edu/programs/AllAboutBirds/BirdGuide/
to hear sounds of the Cooper's Hawk (it's really annoying that this site doesn't convert URL's embedded in posts to links.)

Here is a link that might be useful: Goshawk recording