Eldon, thanks for pointing me at 1690. Reviewing my overnight recording I didn't hear CHTO (or maybe I did, see below) but I did hear a "1690 WVON" ID a half-dozen times and some intelligible English talk a couple of times. Fortunately WVON IDs often, as it didn't fade in for very long when it did fade in. This is my third Chicago station, and the two latest new-for-me W calls have been from Chicago (the previous was WBBM 780).
I heard a few top of the hour KFSG IDs but each was garbled. I didn't hear any other IDs behind it. KFSG was the signal which faded up to recognizable talk and music the most often.
At one top of the hour when I didn't hear KFSG I heard a "KDZZ" call instead. That's new for me too!
Only once did I hear what was clearly a C call but the letters were not distinct and it faded quickly. All that was clear was the C and the O, the middle two were not intelligible. If I didn't know CHTO was there I couldn't identify it. It could even be CJLO.
Sadly, tonight KFSG is dominant.