Interpreters have always played a significant role in the creation, performance practice, distribution, and reception of compositions. This makes them central figures in music creation, a fact that musicology has only recently recognized as an independent subject of research. This publication focuses on three interpretive personalities from the immediate and broader context of the Darmstadt Summer Courses for New Music: singers Cathy Berberian and Carla Henius, and actor and vocal artist Roy Hart. Each has notably influenced the vocal repertoire of their time—whether through their specific vocal abilities and working methods or as initiators and commissioners. This repertoire often raises practical performance questions: How can compositions that were created as vocal portraits of a singer or that may only be realizable by a single person be interpreted? What relevance does this historical repertoire have in the present, and how is the framework of interpretation defined within it? What can interpretation achieve—not as a servant to a supposed authorial instance or as a medium for clarifying research findings, but as an independent epistemic technique? This volume aims at two things: firstly, to illuminate specific historical contexts and apply the insights generated from them in music research and practice; secondly, to illustrate music practice in its potential as a knowledge-generating process. Both aspects unite in the understanding of interpretation as a creative practice.