  We investigate electroproduction of pion pairs on the nucleon in the
framework of QCD factorization for hard exclusive processes. We extend previous
analyses by taking the hard-scattering coefficients at next-to-leading order in
$\alpha_s$. The dynamics of the produced pion pair is described by two-pion
distribution amplitudes, for which we perform a detailed theoretical and
phenomenological analysis. In particular, we obtain constraints on these
quantities by comparing our results with measurements of angular observables
that are sensitive to the interference between two-pion production in the
isoscalar and isovector channels.
