[2][3] It is the only complete listing of all medieval and early modern manuscripts of European polyphonic music.

It is founded on a digital archive of images of European medieval and early to high-Renaissance polyphonic music ranging from complete manuscripts to fragments.

The project has recently benefited from collaborations with two AHRC-funded projects: Sources of British Song (contributing images of manuscripts of monophonic song c. 1150-1300.

DIAMM relies primarily on grant funding and donations from users for its maintenance.

It has recently founded DIAMM Publications, which produces high-quality colour facsimiles of manuscripts in the image collection accompanied by academic introductory studies by leaders in their fields, without the considerable markup of conventional publishers.