Glueball singularity,flavour loops and the Harari-Freund picture

We discuss several points concerning the structure of the cylinder term in the dual topological expansion. Using dual field theory as a guide, we concentrate on the possibility of a two-singularity scheme à la Harari-Freund. We start from results obtained previously at the lowest order in ?=N _f /N _c and study what can be the role of flavour-loop corrections in the real world where ?～1. It is argued that, in spite of the actual value of ?, precise mechanisms exist which can weaken the role of the flavour-loop corrections in the kinematical region where “soft” dynamics dominates. We also claim that theS-matrix at largeN _c (?≈-0) incorporates already many realistic features, and we refute some objections recently raised against the Harari-Freund picture.