Most heritage musical instruments are not played anymore for conservation reasons. Most of the time, each instrument is the only representation left of a style or a historical period. This is coherent with the museums’ task, which is to present diversity in makers, making processes, materials, etc. It is thus interesting to study not only an instrument but also its evolution according to music history or to technical evolution. Studying the whole production of a maker allows a better understanding of his know-how and his technical evolution. Nevertheless, the museum audience has no way to evaluate the acoustical properties of these historical instruments except when a copy (or fac-simile) is ordered. This paper intends to apply a global vibrational analysis on the harp corpus of the Musée de la musique to understand the consequences on the potential acoustical behaviour of the different construction techniques used by two famous harp makers, Erard and Cousineau. The idea is to survey the whole corpus, using the least invasive techniques which are still effective when applied to instruments in a conservation state and to define a vibrational descriptor able to represent different making strategies from the acoustical point of view. Whereas usual descriptive measurements do not discriminate Erard and Cousineau harps’ acoustical behaviours, vibrational measurements, which are strongly influenced by construction techniques, do give this possibility.