Writing for solo instruments today offers composers an option to create a framework that results from the psychoacoustic interaction of composer, listener and performer. The interaction between musicians, audience and the concert environment, and the extent to which they themselves embody the material of the music presented, can be called into question and a composer's expectation of the dynamics of the concert situation is part of this examination. This understanding in turn prepares the way for one of the ultimate challenges and achievements for a composer, writing an opera. Opera combines all the other arts with the composer in command, which is not the case when composing for dance or providing auxiliary music for theatre. Writing an opera means that all features of structure and timing are in the composer’s hands. Opera has had a crisis of identity; the market for traditional operas and classic repertoire but there is no overall identity for contemporary operatic writers. However modern opera is still evolving. This thesis will recount a range of musical ideas developed for a variety of classical solo instruments, all of which attempt to create this interactive concert situation, before going on to consider the three year evolution of my opera The Doll Behind the Curtain.