What is it about Wisconsin that produces so many compulsively productive and offbeat artists? From Baraboo’s Dr. Evermor, to Phillips’ Fred Smith, to Spring Green’s Alex Jordan, to Madison’s own Sid Boyum, what gets into these souls that they feel compelled to create so many strange figures out of scrap metal, concrete and whatever else they have in their backyards? Milwaukee’s Mary Nohl fit right in this pantheon. She spent 50 years converting her home in Fox Point into a peculiar, beautiful world of art. On Thursday, September 19, Milwaukee songwriter Marielle Allschwang brings her tribute to Mary Nohl, “Precession of A Day,” to the Wisconsin Union Theater.