Shift is an input–output mapping where a feature or autosegment loses its underlying associations and surfaces with different associations. In Harmonic Serialism, shift can either be analyzed as a multi-step process or a single-step process. While Gietz et al. (2023) argue for the latter, this paper refutes their arguments and provides evidence supporting a multi-step analysis of shift. Specifically, it demonstrates that shift in Kibondei and Halkomelem, the languages analyzed by Gietz et al. (2023), does not require a single-step shift operation and that the analyses they present are empirically inadequate. Typological modeling not only reinforces the result that a single-step shift operation is superfluous but demonstrates that grammars with such an operation undergenerate with respect to the attested typology.

Harmonic Serialism is a serial version of Optimality Theory in which Gen is restricted to one operation at a time. What constitutes one operation has been a key question in the literature. This paper asks whether shift, in which a feature moves/flops from one segment to another, should be considered an operation. We review three pieces of evidence that suggest so. We show that only the one-step shift analysis can capture the tonal patterns in Kibondei and the segmental patterns in Halkomelem; grammars that rely on spreading or floating features cannot. We complement these findings with a factorial typology in which the one-step shifting grammars predict several attested patterns that the grammars without one-step shift cannot. We conclude that shift must be a single operation in Harmonic Serialism.