In a grown-up world the concept of "play" is diminished and usually reserved for time away from work or business. Yet "play" is the most instructive form of learning and placing things in the context of the world we know.
At a basic level, the sample(s) that you receive as a result of the prototyping process demonstrate the function of the work to date. These samples verify the calculations or provide a tangible proof of some outcome. This is a very necessary and grown-up confirmation of the project.
Hawkshead is strong believer in the necessity of "play" as both a validation exercise and an inventive process. In addition to simply applying "tests" to the prototype it should be used/trialled or, if practical, taken home for others to use. It will soon become apparent if there are any opportunities to improve or add features. In some instances there may be additional “user errors” that can be trapped and avoided.
More often than not the samples show what users value and this is not always where the greatest effort is employed. In the example of an industrial audio product, the work was naturally focused on the primary function. Users anticipated the function and almost “took it as read” that it would work. Users really appreciated the lack of background noise and the clarity of the result.
These types of outcome only occur from "play" and yet they can be the underlining of product success and a foundation of future marketing.