Luciano Canepàri in his DiPI (Dizionario di Pronuncia Italiana) defines Tuscany, Umbria, Marche, Lazio and Rome as “regioni standardizzanti” (regions where a standard-like pronunciation of standard Italian is used), and separates Rome from Lazio, as the capital has some peculiar characteristics, closer to those of Tuscany.
Those regional pronunciations are similar to each others, as are the respective local dialects. There are historical reasons for it. However, one has to point out that, although they’re close to each others, central Italian dialects such as those of Lazio, Umbria and (part of) Marche must be separated from the Tuscan dialects.
The Tuscan pronunciation of standard Italian shows the following features:
- Tuscan gorgia: /k/, /t/ and /p/ between vowels are pronounced as fricatives, that is [h] (similar to the ‹h› in hard), [θ] (similar to the ‹th› in thanks), [ɸ] (hard to find an English comparison here, just see this Wikipedia entry about this sound). If you are curious about the origins of this phenomenon, take a look at this essay (in Italian).
- Weakening of /dʒ/ (for gelo) and /tʃ/ (for cena) between vowels, which become [ʒ] and [ʃ] respectively.
- Affrication of /s/ after /l/, /n/, /r/: borsa becomes bor[ts]a. That feature is not common everywhere in Tuscany.
The features of the central Italian pronunciation (that of Umbria, Marche, Lazio and Rome) are pretty much the same, except for the gorgia, which is typical of the Tuscan dialect only. Also, central Italian people tend to pronounce /b/ as [bb] and /dʒ/ as [ddʒ] between vowels: e.g. abete is pronounced as abbete; progetto as proggetto.
The Romanesco dialect has also some other minor features, such as a slight sonorisation of /t/, /p/ and /k/, so andato might sound vaguely similar to andado to an untrained ear.
The Italian pronunciation in Tuscany, Umbria, Marche, Lazio and Rome — and in the southern regions as well, but that is unrelated here — also includes the syntactic gemination.
It’s important to remark that those features are only regional, and are not part of the standard Italian pronunciation, except for the syntactic gemination. In standard Italian, largely an artificial way of speaking only used by actors, newsreaders and dubbers:
- /k/, /t/ and /p/ are always pronounced as such.
- The grapheme ‹g› is always pronounced as /dʒ/.
- The grapheme ‹c› is always pronounced as /tʃ/.
- /l/, /n/ and /r/ + /s/ are always pronounced as such, with no insertion of a dental stop: therefore, borsa is always bo[rs]a and never bo[rts]a.
- The syntactic gemination is always applied, except for the preposition da, the conjunction and adverb come, and the adverb dove. (Da, come and dove only activate the syntactic gemination in Tuscan.)