We have a boatload of crows around here--I've never heard this before. The voice sounds different as well. Can you show me a recording or video of a crow making the rattle followed by the hooo-mwah hooo-mwah sound? I've poked around and can see why the rattle noise might say crow, but wasn't able to turn up anything remotely similar to the rest of the call. Unsure about ravens in this area but will go google for raven calls and listen.
The call came from the same area, with no other noises that sounded anything like this, for 20-30 minutes (or more?) and then was gone. I'd hear a couple calls like this, then a pause, then more calls. There is a river in that general direction, but the call sounded closer. In real life, the hooo-mwah hooo-mwah was more pronounced.
The common birds that I hear all the time are red shouldered hawks and crows. We also have a pair (or more?) of barred owls that just moved back in.