The National Library of the Netherlands and the Meertens Institute in Amsterdam both possess an extensive collection of folk songs and broadside ballads. A large part of these collections was brought together in the early twentieth century by Douwe Wouters (1876-1955) and Julius Moormann (1889-1974).

Wouters and Moormann shared a passionate love for the broadside ballad genre. They published many articles on the subject and remained devoted collectors until their death. The Wouters/Moormann collection now holds around 6000 broadsides with nearly 15,000 songs. The material is highly diverse, ranging from hand-written songs to broadsides, and from piano songs to older (even seventeenth-century) printed songs.

After the Second World War, the bulk of the Wouters collection was purchased by the National Library of the Netherlands. Another part ended up at the Meertens Institute. The similar Moormann collection first went to the museum 'From Musical Clock to Street Organ' in Utrecht, and ultimately also found its way to the Meertens Institute in Amsterdam.

Besides these two major collections, a number of smaller collections were also digitised as a part of this project. They bear either the name of the original collector or the collection's current location.