  We present a model for dihadron fragmentation functions, describing the
fragmentation of a quark into two unpolarized hadrons. We tune the parameters
of our model to the output of the PYTHIA event generator for two-hadron
semi-inclusive production in deep inelastic scattering at HERMES. Once the
parameters of the model are fixed, we make predictions for other unknown
fragmentation functions and for a single-spin asymmetry in the azimuthal
distribution of pi+ pi- pairs in semi-inclusive deep inelastic scattering on a
transversely polarized target at HERMES and COMPASS. Such asymmetry could be
used to measure the quark transversity distribution function.
