Linguistic and cognitive functions of fine phonetic detail underlying sound systems and sound change

• Fourteen studies show that fine phonetic detail is systematically regulated in shaping sound systems. • Fine phonetic detail links production, perception, and learning, sustaining contrasts and enabling sound change. • Sound systems emerge from controlled allocation of continuous phonetic parameters within prosodic structure. • Prosodic structure guides segmental and suprasegmental realization across languages and domains. • Phonetic grammar is a language-specific, system-internal control system shaped by motor, perceptual, and cognitive pressures. This special issue examines how fine phonetic detail participates in the shaping of sound systems. Across fourteen studies, the central theme is that subtle temporal, spectral, and articulatory patterns are not incidental by-products of articulation, but are systematically regulated aspects of speakers’ phonetic knowledge. They provide the means through which phonological contrasts and prosodic structure are realized, maintained, and sometimes reorganized. The contributions show how languages allocate continuous phonetic parameters—such as timing, coordination, voice quality, and nasality—within prosodic domains (e.g., phrases, words, and syllables) and under general biomechanical and communicative pressures. Studies of Irish, Hawaiian, Japanese, and Mandarin illustrate how prosodic structure guides segmental and suprasegmental realization. Work on English, German, Danish, and Cantonese demonstrates how fine phonetic detail underlies patterns of variation and creates potential pathways for change. Production connects naturally to perception and learning: findings from English accent adaptation and Samoan iterated learning reveal how listeners stabilize or reinterpret detail, linking individual processing to community-level patterning. A set of studies on Italian, Korean, English, and L2 German show how prominence reorganizes cues across articulation, interaction, and acquisition, shaping how speakers signal and listeners recover linguistic structure. These studies converge on a view in which fine phonetic detail arises from a central phonetic component (or the phonetic grammar) of linguistic structure—controlled by speakers, shaped by universal motor and perceptual constraints, and continually adjusted through perception and learning. In this perspective, sound systems emerge from the interplay of these regulated patterns, which sustain contrasts, support communication, and open principled routes for change.