I don't know where Peggy Seeger learned to play the banjo.
She had a full blood brother and a notorious half-brother,
both of whom were always associated with playing the banjo,
so she couldn't win for losing, right?

When Ewan MacColl sang with instrumental accompaniment
in their concert tours,
(I heard them twice if memory serves)
it was she who accompanied him, often as not
on guitar rather than banjo.

And her accompaniments, especially on guitar,
were object lessons in how to do it properly:
they sounded so supportive and natural,
no matter how hard she must have worked at them,
that the general accompaniment-ignoring public
was uplifted by them without suspecting anything.

For music students like myself,
who had mentors or teachers coaching them
in how to accompany singers,
it was fascinating to hear and watch her work.