Joe Offer's post of March 5, 2014, poses the question:
did stepmother Ruth Crawford Seeger have any influence/effect
on young Pete Seeger?

I'm looking at the lengthy interview that Pete Seeger granted to the Banjo Newsletter,
to which I provided a link in the thread,
Pete Seeger's Banjo Virtuosity.
There are some quotes pertinent to that question. For instance:

"Up to [the age of about 7 or 8] I had banged on a piano, I'd tootled on a whistle, squeezed on a marimba, but mainly it was piano and organ 'cause that was what was in the house. I learned what an octave was, and a fifth and a third, and what made a major into a minor ...
"Then [at about the age of 16] I started transcribing recordings in the Library of Congress ... That's when I really learned to read music, because I already knew the principles of reading and writing music. Then my step-mother Ruth taught me about sharps and flats, and within a year I was transcribing hundreds of songs."

Here's another from the same interview:
query: How did you learn about harmony?
"I guess you could say it was all around me when I was growing up. My father and mother -- and my step-mother too -- were all very skilled at reading and writing music ... this is how [my father] met my step-mother Ruth Crawford. She came to New York from Chicago to study with him. Soon they were getting along quite well, and I remember them playing Stravinsky's Sacre du Printemps -- this incredibly complicated symphonic piece of music -- with four hands on one piano, with someone else turning the pages for them: what would take a hundred symphonic musicians to do."