Music structure refers to the description of the long term organization of a music piece through a sequence of structural segments. A structural segment can be defined by its structural borders (a start time, an end time) and a label reflecting the similarity of its music content compared to the other segments'. Its duration is typically around 16 s and more. This document presents the music structure estimation system submitted to MIREX's structural segmentation task in 2012. It is composed of three steps : feature extraction, structural border estimation and segment labeling. First, the system produces a sequence of chroma vectors expressed at the snap scale. This sequence is used to calculate a segmentation criterion based on a morphological model of the structural segments. The structural border estimation is performed by searching the segmentation with lowest cost, which combines this criterion and a regularity constraint. The segments are then labeled by clustering according to their similarity, through the minimization of an adaptive model selection criterion.