  We discuss the decay tau^- -> nu_tau pi^- pi^0 gamma in terms of a model with
the correct low-energy structure and with the relevant resonance degress of
freedom. The nontrivial radiative dynamics becomes visible for large photon
momenta only. We use the model to calculate electromagnetic corrections for the
two-pion contribution to hadronic vacuum polarization extracted from
photon-inclusive two-pion decays. The corrections are insensitive to the
details of the model and depend on the pion form factor only. Putting all
relevant isospin violating corrections together, we obtain a shift Delta a_mu =
(- 120 +/- 26 +/- 3) x 10^-11 to be applied to determinations of the anomalous
magnetic moment of the muon from photon-inclusive tau data.
