This conference highlights a compositional approach recovering and developping the hypothesis of an organic principle of the melody. Unlike the usual methods, which differentiates the organization of notes and rhythm, this principle is characterized by a strong structuration binding the notes and their respective locations in time. Its application reveals a representation of melodic objects in a geometrical space, objects called solid melodies, by analogy to the visual space. Thus, melodic objects can be observed and manipulated by mathematical transformation tools which respect their internal structures or, on the contrary, break them. One of the most interesting function taking advantage of this musical material, preventing any damage to it, is rotation. Its interest is multiple in composition: first, it generalizes the four symmetrical forms used in traditional counterpoint, second, it allows a meticulous understanding of melodic objects, facilitated by the simplicity of the processes used. Finally, this function allows a musical kinematics with succession of images obtained by rotations of an unique basic object. The comparison between visual space and sound space becomes a fertile source for the construction and the manipulation of new sound buildings.