The letters of Marie-Anne de La Trémoille, Princesse des Ursins, married to Duke Flavio Orsini, who headed the francophile lobby in Rome, and those of her sister Louise-Angélique, Princess of Belmonte, wife of Prince Antonio Lante della Rovere, give evidence about all kinds of musical activities, either for private entertainments or for brilliant social gatherings within their palaces. This paper firstly provides a comparative analysis of the two sisters' socio-cultural profile. This case study then documents how women of the aristocracy could try to use their influence within local Roman nobility to support the interests of French monarchy. The last part of the discussion focuses on the theatrical, musical and dance preferences of the two sisters so as to estimate the atavism of their "national" background and to see how each of them organized her patronage in an original way.