"The heart of the collection was collected by the Danish engineer and guitar player Thorvald Rischel (1861-1939)... Another part of Rischel's collection derived from the Danish guitar player J.G. Holm, who had also been a friend of Coste, and from P. Schulte, a Swede who had owned most of the handwritten works by Coste in copies revised by Coste himself. Rischel also acquired all the available compositions for guitar by Fernando Sor, many of them in rare first editions, and a great deal of unpublished music by J.K. Mertz.
After Rischel's death in 1939, his collection of music was dispersed. Most of it came to the librarian and guitar player Frederik Birket-Smith (1880-1952). The rest of the collection was delivered to the Royal Library in Copenhagen. After Birket-Smith's death the Royal Library received the joint collections of Rischel and Birket-Smith."
(From Larson/Danner Catalogue. History of the Collection.)