The fields of marketing strategy in general and new product development in particular appear to assume that marketing strategy should occur by first composing a plan on the basis of a careful review of environmental and firm information and then executing that plan. In this article, we question this assumption by suggesting that there are cases when the composition and execution of an action converge in time so that, in the limit, they occur simultaneously. We define such a convergence of composition and execution as improvisation and suggest that the narrower the time gap between composing and performing (or planning and implementation), the more that act is improvisational.