In the early nineteenth century, concert reviews often judged pianists and pianos on their combined value. This critical tendency is exemplified in the professional career of virtuoso pianist Anna Caroline de Belleville. This article examines the reciprocal relationship between Belleville and her pianos — particularly Érard’s and Streicher’s — within the contexts of the technological development of piano-making and piano performance culture. I argue that the distinct advantages of Belleville’s pianos helped her develop a well-rounded pianism that combined both brilliancy and lyricism, winning her a place among the most distinguished pianists of the day. Furthermore, Belleville’s active engagement with and promotion of her pianos enhanced the instruments’ own reputation and commerciality. This understudied yet illuminating story about the interdependency of the virtuoso and her instruments (and attendant instrument makers) enriches our understanding of nineteenth-century performance culture by highlighting the inextricable relationship between technology, virtuosity, commerciality, and entrepreneurship.