Modal observations of a piano soundboard are compared with results predicted by a model consisting of weakly coupled homogeneous sub-structures. The model is entirely determined by the coarse geometry of the soundboard (main plate, ribs, bridges, cut-off corners) and by the elastic parameters of the wood species. It can also be used to predict the point-mobility at the bridge (where strings are attached) or far from it. The agreement between observations and model predictions is excellent, both in the low- and high-frequency regimes (respectively below and above approximately 1 kHz). Applications include a comparison between the characteristics of different pianos as well as the influence of the wood properties on the point-mobility. Some consequences in terms of acoustical radiation will also be presented.