The main objective of this thesis is to understand the mechanics of a grand piano soundboard and to investigate the influence of several parameters on its modal and vibrational behaviors. Various analysis techniques are made possible by a development of a fully parameterized Finite Element model of the soundboard which allows the user to modify most geometric and material parameters. In addition, two crucial features, namely crowning and downbearing, are included in the model and their individual and combined effects are observed. This study also accounts for the influence of geometric nonlinearities due to downbearing. The piano soundboard includes a large number of unknown factors stemming from its construction process and the material properties of the wood. This thesis uses sensitivity techniques to investigate the influence of various factors on the variability of the modal outputs (i.e., natural frequencies and mode shapes). The different aspects of the model are described in details and various sensitivity methods are tested in this context.