The paper discusses some of the problems of music-theatre with reference to the author's compositions Fidelio (1977), Tuba Mirum (1979) and Pastorale (1980). Music-theatre is defined. Its principal practical problem, that of making the image musician - playing -instrument theatrically significant, is to be solved by placing the performer in a theatrical situation, defined by staging, costume and props (rather than through verbal cues) as in Performance-Art. At a deeper level, the elucidation of meaning through musical structure is compared with the iconic use of imagery. The problem of consciously constructing icons is raised, with practical examples given. The integration of musical and visual structures is discussed, with examples of different approaches. In conclusion it is noted that all the pieces discussed deal with change, and aim to achieve a changed in the audience's perception of the piece, during the performance.