Sound change and coarticulatory variability involving English /ɹ/

English /ɹ/ is known to exhibit covert variability, with tongue postures ranging from bunched to retroflex, as well as various degrees of lip protrusion and compression. Because of its articulatory variability, /ɹ/ is often a focal point for investigating the role of individual variation in change. In the studies reported here, we examine the coarticulatory effects of alveolar obstruents with /ɹ/, presenting data from a collection of sociolinguistic interviews involving 162 English speakers from Raleigh, North Carolina, and a pilot corpus of ultrasound and lip video from 29 additional talkers. These studies reveal a mixture of assimilatory and coarticulatory patterns. For the sound changes in progress (/tɹ/ and /dɹ/ affrication, and /stɹ/ retraction), we find increases over apparent time, but no effect of covert variability in our laboratory data, consisting mostly of younger talkers. When a sound change has already become phonologized to a new phonemic target with a correspondingly different articulatory target, the original variability is obscured. In comparison, post-lexical coarticulation of word-final /s z/ before a word-initial /ɹ/ more closely resembles /s z/ in tongue posture, with an effect of anticipatory lip-rounding that introduces a low-mid frequency spectral peak during the sibilant interval, and greater reduction in the frequency of this peak for talkers who transition more rapidly to the /ɹ/. In order to uncover the role of covert variability in a sound change, we must look to sounds that exhibit synchronically stable articulatory variability