Conversation so far:
who sang vocals on saturday in the park
The song Saturday in the Park contains lead vocals by Robert Lamm and Peter Cetera.
how did the song saturday in the park do
The song Saturday in the Park was very successful upon release, reaching No. 3 on the Billboard Hot 100.
when was the song saturday in the park recorded
The song Saturday in the Park was recorded in September 1971.
The genre of the song Saturday in the Park is soft rock.
https://en.wikipedia.org/wiki/Saturday_in_the_Park_(song)

Question: where did the genre come from
Self-contained rewrite: where did the genre soft rock come from