Student or Learner
"That's right," Mark said. He spoke with self-mocking intentness and a faint familiar accent that reminded David of his father's voice, low and melodic.
"I'm not being hostile," David said, realizing even as he spoke that he was. Realizing, too, that he was beginning to flatten and extend his own vowels, called by the deep pull of language, patterns of speech as familiar and compelling as water.
(The Memory Keeper's Daughter, Kim Edwards)
Would you be so kind to clarify what was meant by the part in bold?
Language is like that. In this case - I'm guessing, from the context of the book's title - thee speaker is unconsciously adopting speech patterns used at a home he's left; or - quite to the contrary - his speech patterns are emphasizing his remoteness from that past. He says 'I'm not being hostile', but his voice tells a different story.
That's one man's view (mine). The good thing about metaphors is that they make you paint mental pictures; others may not agree at all...