The criterion of independence is involved also in breaking down such long contours as can be shown […] to be successive repetitions of the same shorter contour (or of a few different short contours). We may find a short utterance with one short contour over it ('I’m not coming.'), a longer utterance with the same short contour given twice over it ('I’m not coming. It’s too late.'), a longer utterance yet with the same contour three times over it, and so on. The number of occurrences of the short contour depends on the length of the utterance and on the repetition of a particular sequence of morpheme classes (construction […]) under each of the short contours. We therefore say that the two-fold and three-fold repetitions of the short contour are not morphemically independent. For each utterance length and utterance construction there is only one set of independent short contours (. and ? and so on), and repetitive successions of these are not new independent morphemic elements, but merely sequences of the original contour elements.
- Harris (1951), a pag.170, n.32

The length of environment over which independence of 'X' in respect to 'Y' is examined may vary with our immediate purpose (e.g. shorter for determining phonemes, longer for determining morphemes). The handling of partial dependence may vary. In one case, when we seek a first approximation, we may set up partially independent segments as distinct elements. Later, we may return to the same segments and extract a common element which expresses the degree of dependence of one upon the other, having residual elements which express the degree of independence of the segments in respect to each other […]. The criterion of independence thus determines not only the segmentation of our representation into sucessive or simultaneous portions, but also the setting up of abstract elements which can not be readily identified in terms of acoustic or physiological records but which express particular features of the complex relations among the segments or the other elements.
- Harris (1951), a pag.367, n.8