Over my year-and-a-half to two-year study of Basque, I have noticed some pronunciation rules that no course or any book (in English at least) would ever teach you. This thread will contain the various rules I have observed in spoken Basque. Unfortunately, my memory is pretty bad, so I can't think of all of them at this time. But over time I will add more, and anyone else is welcome to post any observations they made.
Rule 1: Nasalization of vowels followed by "n" before "z" and "s"
This rule is pretty self-explanatory, but I'll give some examples, along with a recording.
Example 1: "janzten", present participle of "jantzi", to dress.
Example sentence: "Zer janzten duzu?" What are you wearing?
Pronunciation: [zeɾ ˈxãs̻ten duˈs̻u]
Example 2: "joan zen", past participle "to go" and 3ps. "was"
Example sentence: "Parisa joan zen duela hiru aste." He/she/it went to Paris three weeks ago.
Pronunciation: [paˈɾis̺a ˈxʷã s̻en ˈðu̯ela ˈiɾu as̺ˈte]
Example 3: "irensten", present participle of "irentsi", to swallow
Example sentence: "Amua irensten duen arraina bezala" Like a fish that swallowed a hook
Pronunciation: [aˈmua iˈɾẽs̺ten ˌðuen aˈraɲa βeˈs̻ala]