Canada, Alberta - Unseen bird calling from ground along creek in agricultural area (1 Viewer)

I have been hearing this call this morning, bt I can not get a sighting of what it might be. It seems to be calling from within a stand ofwillow and tall grass that is along a small creek inbetween a couple of fields of wheat , south of Edmonton.
There is also a Song Sparrow calling in this recording but the louder call is what I am trying to figure out.
Thanks,
z.

The loud call is that of a Sora.

Thank you. That is a new bird for me in this locationo