  We study the mismatch between a full calculation of non-global
single-logarithms in the large-N_c limit and an approximation based on free
azimuthal averaging, and the consequent angular-ordered pattern of soft gluon
radiation in QCD. We compare the results obtained in either case to those
obtained from the parton showers in the Monte Carlo event generators HERWIG and
PYTHIA, with the aim of assessing the accuracy of the parton showers with
regard to such observables where angular ordering is merely an approximation
even at leading-logarithmic accuracy and which are commonly employed for the
tuning of event generators to data.
