Monuments of Music are large anthologies of music that collect music of a particular country, genre, or time period. They often include music that is not otherwise available, and may be your only source for a particular work. Editing practices of monuments have varied, but later editions tend to be done as critical editions and present reliable versions of the music.
Some of the most important monuments in RBI are national sets that document the music of a country or region. These include Monuments of German Music (Denkmäler Deutscher Tonkunst), Monuments of Austrian Music (Denkmäler der Tonkunst in Österreich), and Musica Brittanica.
Other large sets are collections of a time period or genre, such as Corpus of Early Keyboard Music, Early English Church Music, and The Symphony.
Monuments of Music are shelved, along with smaller anthologies, in M2. Most of of them are in RBI and are for use in the library. Jones Library does have several monuments and many other anthologies that can be checked out.