Seventeenth-century French that kept going on its own for three hundred years. The most audible feature is affrication: t and d become ts and dz before i and u. High vowels lax in closed syllables — 'vite' is closer to English 'vit' — and the long vowels of old French survive as diphthongs. The nasal vowels sit higher and further forward than in Paris, and all four are still distinct.
Where: Québec, Canada
The way in: 'Tu dis' as t͡sy d͡zi, then relax the i in 'vite' to English 'vit'.
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Anything the spelling engine can transcribe, the accent can move. Slow it down to hear the shape.
A wider pitch range than Paris, with stress that can fall earlier in a phrase. Older speakers keep an apical, rolled r; younger urban speakers use the Parisian uvular one.
What moves, one rule at a time
In the order the mouth applies them. Every before-and-after is playable — click the IPA. The pattern is the rule as the engine runs it, for the curious.
Consonants
t and d hiss before i and u
t(?=[iyɪʏjɥ]) → t͡s
When: before i, u, or the glides j and ɥ
How: Say the t and let it turn into an s as you release into the vowel. 'Tu' is 'tsu'.
The tongue is already high for the vowel, so the stop leaks into a hiss on release. It is the single most reliable marker of a Québec speaker.