The theory of harmonic vectors identifies the asymmetry of root progressions as one of the outstanding characteristics of tonal harmony. One of the possible origins of this phenomenon is the treatment of the dissonance — where the rules of preparation and resolution have repercussions on harmonic sequences. This paper seeks to determine if the evolution of the treatment of the dissonance, along with the change of the aesthetic paradigms from prima pratica to seconda pratica, is to be considered as one of the main causes of asymmetrical progressions and could have contributed to tonal syntax. This evolution is described on the basis of Christoph Bernhard's theory of figures. The paper considers the teleological principle to which the treatment of the dissonance is subject and identifies the elements specific to the use of dissonance that may account for the asymmetry of root progressions in seconda pratica. Two examples, one in stylus antiquus and the other in stylus modernus, show the correlation between extra-musical references, the usage of dissonances and the direction of the harmonic progressions, both in the overall statistics and in the local fluctuations of asymmetry through the work.