  The effects due to soft-photon emission (and the related virtual corrections)
in multi-body decays of B, D, and K mesons are analysed. We present analytic
expressions for the universal O(alpha) correction factors which can be applied
to all multi-body decay modes where a tight soft-photon energy cut in the
decaying-particle rest-frame is applied. All-order resummations valid in the
limit of small and large velocities of the final-state particles are also
discussed. The phenomenological implications of these correction factors in the
distortion of Dalitz-plot distributions of K -> 3 pi decays are briefly
analysed.
