In 1929, the library of the Conservatoires royaux de Bruxelles acquired the Sainte-Gudule collection thanks to the work of the librarian Charles van den Borren (1874-1966). This collection is clearly important for both musical reasons and as important heritage items. The collection consists solely of works dating between the end of the seventeenth and beginning of the nineteenth century, including a little over 500 music manuscripts and a few printed ones. This collection essentially comprises religious music although there are a few instrumental works as well.
This unique collection of music is also reflective of the activities of the Canon Jan Bernard Vanden Boom (1688-1769), cantor of the Brussels Cathedral of Saints Michel and Gudule, and also a sponsor and person in charge of the music library. Vanden Boom was born in Brussels and became interested in music at an early age, and it was during a stay in Italy in 1725 that he discovered the music of Vivaldi. He became cantor at the cathedral in 1736 and played an active role in the musical life there: he helped develop the instrumentation of the music, hired talented musicians to play, and ensured that they had both scores and good quality instruments available. Vanden Boom was also in charge of the collection of music manuscripts and he oversaw the purchase or transcription of copies of existing pieces of music. He had works of the Italian masters copied, and also commissioned new compositions from the cathedral choirmasters, first Joseph-Hector Fiocco (1737-1741) then Charles-Joseph Van Helmont (1741-1777). For this reason, the collection contains both copies and autograph works, including a number of works by Hercule-Pierre Bréhy, Henri-Jacques de Croes, Henry Du Mont and Jean-Noël Hamal alongside Francesco Durante, Giovanni Pergolesi or Pietro Torri.
Faced with this growing number of works, towards the middle of the eighteenth century, Vanden Boom started to organise and classify the manuscripts. He chose to cover each manuscript with a hardcover (33 x 21cm). The covers are decorated with a beautiful decorative motif which depics a frame of stylised leaves, with flowers at the bottom and decorated with various musical instruments at the top. On the inside of this frame, Vanden Boom wrote the title of each work, plus the instruments for which it was written, the name of the composer  and the number of scores in each folder. The decoration is all the more unique for the fact that the upper part of the decoration on each document features an open scroll on which Vanden Boom has noted by hand the main musical motif of the piece. As for the lower part of the decoration, this consists of a medaillon decorated with two masks in the centre of which is engraved the text "A. R. D. VAN DEN BOOM CANT :". So it is clear that Vanden Boom was behind the initative to assemble the works in the Sainte Gudule collection and to take such care over their conservation. After this, each item has been given a numerical classification and a label with a number has been attached to each folder. This collection which ultimately is a record of two centuries worth of musical activity in Brussels, is today conserved both in the library of the Conservatoires royaux de Bruxelles as well as the Royal library of Belgium.
 Regarding the name of the composer, the folder made by Vanden Boom features the name H. J. Croes, whereas on the manuscript itself, this name is written H. J. De Croes.