
The four R projects emerged from the efforts of scholars, archivists, librarians, and musicians to create research tools that provide access to key sources of musical heritage and culture. These sources include musical works preserved in manuscripts and printed editions, historical and contemporary writings on music, and visual representations of music and musical performance. Recognizing that a vast body of music-related literature and iconography remained largely unexplored, the International Musicological Society (IMS) and the International Association of Music Libraries, Archives and Documentation Centres (IAML) jointly sponsored the development of the R-projects. The purpose was to create bibliographic research tools that identify, document, and facilitate access to this extensive collection of primary sources.
Below are short descriptions of the four R projects:

The Répertoire International des Sources Musicales (RISM), or International Inventory of Musical Sources, is dedicated to identifying, documenting, and providing access to musical sources worldwide. Through a network of independent national working groups, RISM catalogs printed music published before 1800, music manuscripts dating from after 1600, as well as libretti, theoretical treatises, and other music-related documents. These records are consolidated and standardized by the RISM Zentralredaktion (Central Editorial Office) in Germany, before being prepared for publication.

The Répertoire International d’Iconographie Musicale (RIdIM), or International Inventory of Musical Iconography, based in Switzerland, is dedicated to documenting and studying visual materials related to music, dance, theatre, and opera. To support research in musical iconography, RIdIM publishes catalogues, scholarly studies, and a newsletter and sponsors the annual scholarly yearbook Imago musicae, published in collaboration with Libreria Musicale Italiana.

The most recent of the four R-projects is the Répertoire International de la Presse Musicale (RIPM), or Retrospective Index to Music Periodicals (1800–1950). Established in 1980, RIPM was created to provide comprehensive access to historical music periodicals and to promote research based on this rich but often overlooked body of documentary evidence. By indexing and making available music-related journals and newspapers, RIPM has become an essential resource for scholars investigating the musical, cultural, and intellectual history of the 19th and early 20th centuries.

Répertoire International de Littérature Musicale (RILM) publishes a range of digital resources that support the global music research community. Its flagship publication, RILM Abstracts of Music Literature, is a comprehensive bibliography of scholarly and professional writings on music. Other resources, such as the RILM Index to Scores and Collected Editions (RISE), provide digital tools for locating specific musical works within collected editions, anthologies, and series. RILM also offers specialized reference and archival resources. The RILM Archive of Popular Music Magazines (RAPMM) is an extensive and continually expanding digital collection of independently published popular music magazines and fanzines, spanning the late 1960s to the present. RILM Music Encyclopedias brings together a growing collection of full-text music reference works, while DEUMM Online provides access to the most comprehensive modern music dictionary in the Italian language. In addition, RILM hosts MGG Online on its platform, offering authoritative and up-to-date information on a wide range of music-related topics, including musicians, genres, historical periods, and scholarly concepts. RILM also now owns the Hofmeister XIX database.

