In this work we propose the construction of confidence bands for Kendall plots, based on asymptotic confidence intervals for quantiles of Kendall's distributions. The main application explored here is from the linguistic field. We analyze specifically the relationship between values of the acoustical correlate ` fundamental frequency' (F-0) of pretonic syllables perceived as bearing secondary stresses and values of other pretonic syllables adjacent to those, in Brazilian Portuguese (BP) and European Portuguese (EP) data. Our hypothesis is this relationship can be a cue to the secondary stress perception by BP and EP speakers. From the statistical point of view, we obtained that for the two varieties of Portuguese the dependence is modeled by Gumbel's copulas.1648