One of the more surprising results of the use of artificial neural networks in the analysis of acoustic perceptions is the regularity of dispositions, on a Kohonen self-organizing map, of chord images: in fact these images clearly show the bent to spontaneously dispose themselves along closed, circular patterns reminiscent of the circle of fifths. In this paper we firstly reproduce these results and then test them against the hypothesis that the regularity of patterns could be the effect of the preprocessing and of the circular transpositions of the original signal images, rather than of their informative content referred to the tonal relations among the chords.