Polifonia implements a digital ecosystem for European Musical Heritage: music objects along with relevant related knowledge about their cultural and historical context, expressed in different languages and styles, and across centuries. The ecosystem will include methods, tools, guidelines, experiences, and creative designs, openly shared according to F.A.I.R. principles. The aim is to provoke a paradigm shift in musical heritage preservation, management, studying, interaction, and exploitation. Ten pilots, spanning from historical bells and organ heritage, classification of polyphonic notated music, to the historical role of music in children's lives, will drive the development of the ecosystem through continuous validation of its technologies. The Web, its standard formats and protocols are used as its reference architecture. Knowledge graphs are the enabling technology for integrating, representing, and interlinking music-related data with heterogeneous and distributed provenance. Dedicated research in Semantic Web, Data Science, Machine Learning, Language Technologies, and Human-Machine Interaction will enable discovery and automatic analysis of massive data, as well as their reuse for research, consumption and promotion. The project is conceived by an interdisciplinary team of passionate researchers and curators: computer scientists, anthropologists and ethnomusicologists, historians of music, linguists, musical heritage archivists, cataloguers and administrators, and creative professionals. They bring real-world use cases to define the ten pilots. The planned dissemination and exploitation actions allow the creation of a stakeholder network since the early stage of the project. Specific initiatives address societal and economic challenges: increased accessibility to musical heritage for people with disabilities; reproducible and sustainable creative designs for promoting musical heritage; increased engagement of young female students in STEM curricula.