SEAM: Spectral Embedding Alignment and Merging for Low-Resource TTS

Walaa Othman, Baher Mohammad, Stamatios Lefkimmiatis, Ammar Ali


Abstract
Expanding the vocabulary of conditional text-to-speech (TTS) models typically requires extensive fine-tuning with paired audio, creating a major bottleneck for low-resource and cross-lingual adaptation. To address this, we introduce SEAM, a zero-audio initialization method that constructs embeddings for unseen tokens from known subtokens. Unlike standard pooling strategies that ignore sequential structure, SEAM applies a spectral filter to preserve temporal phonetic order and uses closed-form ridge regression to align the new embeddings with the pretrained conditioning manifold. Across three languages and two TTS architectures, SEAM matches baseline performance using up to four times less training data, reducing sample complexity by 75% compared to random initialization and mean pooling. Our approach provides a lightweight, reproducible, and theoretically grounded solution for vocabulary expansion in low-resource speech synthesis.
Anthology ID:
2026.findings-emnlp.254
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
5336–5347
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.254/
DOI:
Bibkey:
Cite (ACL):
Walaa Othman, Baher Mohammad, Stamatios Lefkimmiatis, and Ammar Ali. 2026. SEAM: Spectral Embedding Alignment and Merging for Low-Resource TTS. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 5336–5347, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SEAM: Spectral Embedding Alignment and Merging for Low-Resource TTS (Othman et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.254.pdf