In Arthur Miller's Death of a Salesman, what does Willy's father symbolize?

This is in fact incorrect. The man you refer to is Dave
Singleman-a salesman acquaintance of Willy's who he blindly emulates for having so many
sales 'correspondences' which Willy takes to mean friends. Willy has little memory of
his actual father, except the flute song that he hears in lucid moments and Ben's
assurance that he was a travelling salesman who sold flutes. The significance of Willy's
father therefore are threefold:

a) He symbolises Willy's
longing to escape, travel and live a simple life e.g. selling flutes-and his inability
to understand this desire. He considers his father to have been successful despite him
only ever having sold simple instruments.

b) He symbolises
Willy's core self-doubt because he was abandoned as a child. He so needs a father figure
to guide him on the right path and yet can remember nothing but loneliness. Perhaps this
is why he abandons his own sons.

c) He symbolises the great
'secret' of sales which Willy longs for, and is in fact imaginary. He presumes his
father must have had it, and is tortured by its being just out of his reach. In fact, he
just needs to have more work discipline.