  This paper presents an analysis of pi- Pb -> X- Pb -> pi-pi-pi+ Pb events at
190 GeV/c beam momentum and very low four-momentum transfer t'<0.001 GeV^2/c^2.
Coherent scattering off the nucleus as a whole dominates with contributions
from Reggeon, Pomeron and photon exchange. The latter originates from Primakoff
reactions and is identified by the sharp Coulomb peak of intensities at t'
approx 0. The partial-wave analysis of these data focusses on new techniques
for the extraction of the Primakoff contribution at low masses. Its measured
absolute cross-section at sqrt(s) < 5 m_pi is well in agreement with the
prediction from chiral perturbation theory.
