Répertoire International des Sources Musicales (RISM) was established in 1952 by the International Musicological Society and International Association of Music Libraries. The aim of RISM is to locate and catalogue all surviving musical sources dating from the earliest times to about 1850, and in doing so to bring them to the attention of a much wider public.

Thirty-two countries are now working to catalogue source material in their libraries and archives, using the standards laid down by the RISM Central Office. RISM's remit includes printed and manuscript music, works of music theory and libretti. The catalogues produced have become established as primary research tools for music, and are used worldwide by academics, students, performers and others to trace and identify music materials.

The UK's contribution to RISM is overseen by the RISM (UK) Trust, which was also historically responsible for documenting music source material in Dublin. An Irish working group has been set up to oversee the collection of data in the Irish Republic and Northern Ireland, and a new list of repository sigla has been drawn up (please see RISM Ireland's webpage at http://www.musicologyireland.com/rism/index.html).

Between the 1950s and 1990s, cataloguers in the UK concentrated largely on documenting printed music, along with manuscripts dating from before 1600. The data was published in RISM Series A/I and B. Work is now ongoing on the cataloguing of music manuscripts from the period 1600 to 1850, a key period in music history and one for which much significant material is held in the UK. That data is being made available via this website, as Music Manuscripts after 1600 in British and Irish Libraries.

A complete list of RISM library sigla may be downloaded in PDF format from the RISM Central Office website at http://rism.ub.uni-frankfurt.de/bibliothekssigel/BIBVERZ_2008_10.pdf. The sigla list on the UK & Ireland website is a subset of that complete list, representing libraries for which records are currently found in the UK & Ireland database.