Just a brief post to say that, after listening to the recordings on the Kansas Anuran Monitoring Program (http://www.naherpetology.org/kamp/default.asp?page=taxa), I am quite sure that we have boreal chorus frogs (Pseudacris maculata) singing in the draw. They were particularly vocal last night - a bright moon, warm air...ah, they were in the mood for love!
I have also heard the simpler call of the spotted chorus frog (Pseudacris clarkii) during the afternoon earlier this week when the temperatures were a little cooler. They could well be singing along with the boreals in the evening, and my ear would probably not be trained enough to separate the two songs. (Thank goodness I'm usually able to learn visually - I'd be a basket case if I had to rely on my auditory learning skills!)