  I report on some recent work done in collaboration with Santi Peris and Boris
Phily (hep-ph/0007338) where, using the Aleph data on vector and axial-vector
spectral functions, we test simple duality properties of QCD in the large-Nc
limit which emerge in the approximation of a {\it minimal hadronic ansatz} of a
spectrum of narrow states. These duality properties relate the short- and
long-distance behaviours of specific correlation functions, which are order
parameters of spontaneous chiral symmetry breaking, in a way that we find well
supported by the data.
