In the early twentieth century, Alphons Diepenbrock was generally considered to be the greatest living Dutch composer, and certainly the most important since Sweelinck. His orchestral works were performed by Willem Mengelberg and the Concertgebouw Orchestra, and his piano Lieder by the country's most renowned singers, including Aaltje Noordewier-Reddingius, Pauline de Haan-Manifarges, Johannes Messchaert and Gerard Zalsman. Whenever a new work of Diepenbrock's was premiered, the papers were always full of preliminary analyses beforehand, and reviews afterwards. Shortly after 1900, the first essays appeared on his works, such as those in the collection titled Muzikale fantasieën en kritieken (‘Musical Fantasies and Reviews’) by J. C. Hol. The interest in his music continued unabated after his death, and not only during the commemorative celebrations held in 1946 and 1962. After Balthazar Verhagen and Elisabeth Diepenbrock established the Alphons Diepenbrock Foundation in 1921, the young musicologist Eduard Reeser devoted himself to the preservation of Diepenbrock's legacy. The composer's larger works also appeared in print, and Alphons Diepenbrock became a definitive part of the Dutch musical canon.

In 1935, Eduard Reeser wrote a concise monograph on Diepenbrock, followed by a brief account of his life and works in the pocketbook series ‘Neerland's Muziekleven’ (‘Musical Life in the Netherlands’) in 1944. In 1980, a more comprehensive biography by Wouter Paap was published. Between 1962 and 1998, in collaboration with Diepenbrock's younger daughter, Thea Vermeulen-Diepenbrock (and after her death in 1995, with the support of her daughter Odilia Vermeulen and Ton Braas), Eduard Reeser released the Brieven en Documenten (‘Letters and Documents’) of Alphons Diepenbrock in a series of ten weighty volumes. Although the results of this gargantuan labour – and of the extensive accompanying annotations in particular – provided me with an indispensable collection of source materials, they also forced me to make many difficult choices, as the attached chronology provides an almost daily account of the life of Alphons Diepenbrock. In the preface to the eighth volume of Brieven en Documenten, Reeser revealed that it had been Thea Vermeulen's plan from the beginning for her and Reeser to write a biography consisting ‘partly of excerpts from letters and reviews, and partly of musical analyses’, but in the final years of his life he did not manage to bring this plan to fruition.

I might therefore consider it my ‘lot’ in life that the Alphons Diepenbrock Foundation should have asked me to write a monograph on Alphons Diepenbrock.