The present contribution summarizes a research made by the author over the past ten years on the making of reading scores so as to accompany the hearing of recorded music by Boulez, Stockhausen and Pousseur. Those sources can be written sketches for composition of technical realization leading to "graphic recompositions" by special criteria inherent to the pieces. However, there are also sonic sources allowed to enter the pieces by accumulating partial view points meant to enhance the understanding of the work. The latter sources initiated a reflection on the way how to undertake a new realization of Pousseur's Scambi and eventually led to a reconstitution of a five-channel version of Stockhausen's Gesang der Jünglinge.