Untitled Sighting

We were sitting around a campfire in our yard with our 3 dogs, when we heard coyotes howling-- nothing unusual.  We see tracks and hear them frequently.  The coyotes were howling and were then joined by a lower, deeper howl.  We assumed that it might be a wolf joining in the howling, but authorities deny there are wolves in Illinois, too.  We are experienced outdoor people.  We do a lot of hiking and outdoor activities.  We frequently spend time in northern Wisconsin and have seen and heard wolves in the wild.  This scared us so badly that we went back to the house.  So, we didn't see anything, just the vocalizations.