In this paper two aspects of the vibrato signal characterisation are presented. First, an analysis method, which breaks down the musical signal into its different partials, and decomposes them into two separate contributions: AM and FM. This allows an objective characterization of the vibrato according to musical parameters. Second, a procedure for vibrato synthesis is proposed, based on the previous analysis. Even though the results of the synthesis are not fully satisfactory, they shed new light on the vibrato modeling.