Velar nasal in sound change. On the phonetic origin of Florentine anaphonesis

In Florentine anaphonesis, the lowering of Latin short I and U is blocked in closed syllables whose coda is formed by a velar nasal consonant (It. lingua instead of *lengua). We analyse the degree of contextual nasalization of vowels before /nk/ and /ng/ clusters and show that the properties of the speech signal which might have triggered FA in the past are present as synchronic variation in a laboratory speech corpus produced by contemporary Florentine speakers. Our data additionally explain the observed asymmetries in the distribution of anaphonetic forms in contemporary Florentine Italian lexicon. The degree of contextual nasalization of vowels is shown to depend not only on the properties of the vowels and of the adjacent nasal, but also on the properties of the post-nasal consonant and on the timing relationships within the VNC interval.