Since 2000, the museum has been located in the former Old England department store, built in 1899 by Paul Saintenoy out of girded steel and glass in Art Nouveau style, as well as the adjoining 18th-century neoclassical building designed by Barnabé Guimard.

[3][4][5] Its first curator, Victor-Charles Mahillon, greatly expanded the already impressive collection, and by the time of his death in 1924, the MIM consisted of some 3,666 articles, among which 3,177 were original musical instruments.

He was noted for his astute judgments in obtaining these large collections by calling on philanthropists, mixing with erudite amateurs who sometimes became generous donors, and through friendly relations with Belgian diplomats in foreign posts, who sometimes brought back instruments from beyond Europe.

Ernest is notable for editing several articles on Belgian makers for the National Biography and devoting a long monograph to La facture des instruments de musique en Belgique, which appeared at the 1935 International Exposition held in Brussels.

[5] With the arrival of the esteemed Latinist Roger Bragard, curator between 1957 and 1968, larger budgets became available from the Ministry of Culture, as exhibits were renovated, new personnel were hired, concerts were again organised, and new rare pieces were collected.

[citation needed] The museum's collection presents Belgian musical history (including Brussels' importance in the making of recorders and various obscure proto-synthesizers (Ondes Martenot,[7] Theremin,[8] etc.)