De Vries puts more focus on his own notes to be convincing themselves, instead of the notes being the result of pre-compositional systems (Schneeweisz 10, 11). In this sense he is highly aware of the fact that it is not possible to entirely envision what effect the written notes will have on a listener. His approach towards composition can be described as speculative (Klis 388-389). To be able to give meaning to his written notes, De Vries turned for instance to the symbolism of Baroque techniques, such as the falling motive to illustrate the idea of death. De Vries also turned his attention towards the re-usage of music of the past (Wenekes 30), as exemplified by his "Organum" (1971), in which he re-introduced Perotinus' style in a modern setting.