Phonemes with restricted distribution represent an interesting analytic challenge. Well-known sources include the adoption of certain phonemes from other languages in borrowed words, emerging phonemic splits, and special phonological subsystems (e.g. ideophones). This paper aims to widen our conception of such marginal phonemes, by incorporating another source: specific vocal gestures called into play in interactional settings. Our initial puzzle involves a restricted phoneme set in the Papuan language Nen: two classes of sounds are restricted to interactive contexts, namely interjections and deictics. These sounds are the nasal vowels ã , ẽ , and the glottal fricative h . Several questions arise here. Should these restricted sounds be considered part of the phoneme system? How did they evolve? How does their presence interact with seemingly equivalent sounds in neighbouring languages, in contexts of possible loanwords? We then pass to two other languages where sounds that are unquestionably phonemes have, in at least some phonotactic positions, clear correlations with interactive uses: initial /ð/ in English, essentially restricted to words of person (thou), space (that), time (then), or discourse deixis (the, though), and glottal stops with morphemic function in Bininj Kunwok, restricted to immediate aspect[43], addressee-engaged demonstratives, and kinship vocatives. It is already known that non-phonemic speech sounds (e.g. what is written mhm in English) are used in interaction. This paper proposes that the special phonetics of interaction can integrate further into the sound system and, in such cases as those presented here, either expand the phonological system in absolute terms by adding new phonemes, or expand the phonotactic possibilities of phonemes already occurring in other phonotactic positions.