He focused on Johann Sebastian Bach, his family and his environment, and the chronology of his works.
In 1951 he received his doctorate at the Free University of Berlin with the dissertation Alter Stil und alte Techniken in der Musik des 19.
Von Dadelsen was director of the Johann Sebastian Bach Institute in Göttingen[1] from 1961 to 1993.
As president of the editorial board of the Neue Bach-Ausgabe (NBA), he influenced the second complete edition of Bach's works in a decisive phase.
He wrote books and numerous articles on music history, including some articles of the first edition of Die Musik in Geschichte und Gegenwart (Music in history and present).