GRAFT: Grafted Reference Audio for Fine-grained Pronunciation in Zero-shot Text-to-Speech

Antonis Asonitis; Francesco Verdini; Aref Farhadipour; Vijeta Avijeet; Pierre-Edouard Honnet; Marzieh Razavi; Juan Pablo Zuluaga Gomez

arXiv · 2607.02633

GRAFT: Grafted Reference Audio for Fine-grained Pronunciation in Zero-shot Text-to-Speech

Antonis Asonitis·Francesco Verdini·Aref Farhadipour·Vijeta Avijeet·Pierre-Edouard Honnet·Marzieh Razavi·Juan Pablo Zuluaga Gomez

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Abstract

We present GRAFT, a per-word pronunciation conditioning mechanism for text-to-speech neural codec language modeling. Existing systems reach high intelligibility and naturalness but inherit the ambiguity of text and mispronounce rare proper nouns, loanwords and technical terms. Even phoneme-conditioned models offer no direct acoustic handle for per-word pronunciation. GRAFT controls the pronunciation of a chosen word from a short spoken sample of it, encoded with the model's own speech tokenizer and bound to the word's position in the prompt. Voice conversion during training-data construction disentangles the hint speaker from the target speaker, so the hint may come from any voice while the output stays in the target voice. In a blind English listening study, human raters rank GRAFT first by a clear margin, judging its rendering of the difficult word closest to a reference recording of that word. On a five-language objective benchmark, GRAFT reduces target-word phoneme error rate by 22-39% over the identical text-only backbone and outperforms competitive open-source zero-shot systems, both phoneme- and text-conditioned, on target-word pronunciation, while preserving speaker similarity and naturalness.

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Antonis Asonitis, Francesco Verdini, Aref Farhadipour, Vijeta Avijeet, Pierre-Edouard Honnet, Marzieh Razavi, Juan Pablo Zuluaga Gomez. 2026-07-02. GRAFT: Grafted Reference Audio for Fine-grained Pronunciation in Zero-shot Text-to-Speech. https://arxiv.org/abs/2607.02633

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