Woman with Harpsicord, Silently Playing

Many people online have stated that they think lines six and seven of the Milwaukee Verse are abstract, and a bit of a stretch if you follow people's logic online.  The lines are...

"From woman with harpsicord

Silently playing" 

According to people online, this is a reference to Marietta Robusti, and thus Marietta Avenue, which is located between where you "View the three stories of Mitchell" (line one) and when you "Step on nature, cast in copper" (lines eight and nine).

Marietta Robusti was a painter, and her self-portrait is of her with a harpsicord.  

I am inclined to believe this is exactly what Byron Preiss meant.  The Chicago casque was buried within walking distance of the famous Chicago Art Institute.  He dedicated much of his professional life to the publication of graphic novels.  I would be surprised if Byron didn't have an interest in, and knowledge of, art.