In this paper, we describe the LIA system proposed for the MediaEval 2013 Soundtrack task. The aim is to predict the most suitable soundtrack from a list of candidate songs, given a TV commercial. The organizers provide a development dataset including multimedia features. The initial assumption of the proposed system is that commercials which sell the same type of product, also share the same music rhythm. A twofold system is proposed to provide a music for a commercial: find commercials with close subjects in order to determine the mean rhythm of this subset, and then extract from the candidate songs the music which better correspond to this mean rhythm.