I've been playing around with composition recently (very different from improvisation because of the need to commit something and define it more precisely). Thinking about motifs. I started this piece with a big flourish but little in terms of melodic interest. All the composition textbooks talk about motifs and motivic development. I was always sceptical about this.
In my thinking about prolongation and the essence of a piece, the question seems to be that the motif is a coercive device for prolonging an essence. However, as a coercive device, it also creates conditions for disruption and exhortation. Motivic transformation is a subtle blend of coercion and disruption for example. But the motif can also in itself seem to be essential (think of Reti's analytical technique)?