Abstract An isobar model for the production of pions by 600 MeV protons on nuclei is studied. The higher-energy pions are predicted to come from incoherent nucleon-nucleon production of the (3, 3) isobar in the nuclear surface. One finds considerable sensitivity of the production to the nuclear surface properties. Agreement is found with nuclear surface properties determined by multi-GeV incoherent quasi-elastic scattering of nucleons by nuclei. The results here can be easily generalized for neutron projectiles. It is possible that the incoherent production model studied here will be useful in determining high-energy unstable particle-nucleon total cross sections.