Usually the call is repeated 3 times, occasionally 2 or 4. Then a gap of a few seconds or minutes before it's repeated. Often the direction and distance may change between repeats.Yep, crows seem to have a "call" which is the familiar "caw caw" type croaking. But they also have a kind of "song", usually given from a perch, which consists of some strange muttering, squeaks and also variations on "motor horn" sounds a bit like the one you posted. BTW was it just a three-note only sound, or was there more that has been cut off by the recording?