PL-ModernBERT-gl: Phoneme-level ModernBERT for Galician

Overview

• Model Description
• Intended Uses and Limitations
• Training Details
• Evaluation
• Citation
• Additional Information

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Model Description

PL-ModernBERT-gl is a phoneme-level masked language model trained on Galician text. It is based on the state-of-the-art ModernBERT architecture, adapting the Phoneme-Level BERT (PL-BERT) framework to learn contextualized phoneme representations via masked language modeling and alignment objectives.

This model is designed to support phoneme-based text-to-speech (TTS) systems, including but not limited to StyleTTS2. Thanks to its Galician-specific phoneme vocabulary and contextual embedding capabilities, it can serve as a high-precision phoneme encoder for any TTS architecture requiring phoneme-level features.

Key Improvements & Features:

• Native Galician Pipeline: Unlike the original PL-BERT architecture which relied on English phonemizers, this model integrates the open-source linguistic tool Cotovía for native Galician grapheme-to-phoneme transcription and text normalization.
• 1:1 Alignment System: Implements a strict sequential alignment between graphemes and phonemes, successfully handling Galician digraphs (e.g., ll, rr, ch, nh, qu), silent characters (e.g., silent h), and morphosyntactic contractions (e.g., para + a $\rightarrow$ pra).
• Dual-Head Architecture: The core encoder branches into two parallel prediction layers during training:
  • MLM Head (Masked Language Modeling): Predicts the identity of masked phonemes.
  • P2G Head (Phoneme-to-Grapheme): Predicts the corresponding grapheme for aligned feature extraction.

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Intended Uses and Limitations

Intended uses

• Integration into phoneme-based Galician TTS pipelines (such as StyleTTS2).
• Contextualized phoneme embedding extraction for downstream speech and linguistic tasks in the Galician language.

Limitations

• Not designed for general-purpose word-level NLP tasks (e.g., standard text classification, Named Entity Recognition, or sentiment analysis).
• Strictly supports Galician phoneme tokens mapped through the provided tokenizer utilities.

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Training Details

Training Data

The model was pre-trained on a curated Galician corpus of 11.6 million words compiled from diverse domains under open licenses:

Corpus Source	Domain	Word Count	License
Enciclopedia Galega Universal	Encyclopedic	4,751,813	CC-BY-4.0
URCO Editora	Literature / Novels	1,937,517	CC-BY-4.0
Wikipedia	Encyclopedic	1,794,937	CC-BY-SA-4.0
Mallando no Android	Technology Blog	1,553,327	CC-BY-4.0
Revista Pincha	Culture Blog	669,020	CC-BY-4.0
A Nosa Terra	Journalistic	652,372	CC-BY-4.0
Servizo Publicacións USC	Academic / Scientific	280,858	CC-BY-4.0
Total		11,639,844

Prosodic Enrichment

To capture expressive prosody and speech modulation, the training corpus was enriched with two dedicated subsets of 66,338 interrogative sentences and 11,546 exclamative sentences.

Dynamic Masking Strategy

To force the model to prioritize prosodic clues over highly frequent phonemes, an inverse-frequency dynamic masking algorithm was implemented:

• Common Phonemes: 15% masking probability.
• Standard Punctuation Marks: 40% masking probability.
• Critical Prosodic Marks (!, ?): 80% masking probability.

Training Configuration

Parameter	Value
Model Type / Core Architecture	ModernBERT (12 layers, 12 attention heads)
Hidden Size	768
Intermediate Size (FFN)	2048
Batch Size	64
Total Steps	200,000
Precision	Mixed Precision (fp16)
Initial Learning Rate	1e-4
Scheduler Type	onecycle (Cos annealing strategy, Warmup ratio: 0.1)
Max Sequence Length	512
Replacement Probability	0.2

Evaluation

The model was evaluated using an independent test partition from the core phonemized Galician dataset. Performance was tracked via Masked Language Modeling accuracy (predicting masked phonemes) and Phoneme-to-Grapheme symbolic alignment metrics (predicting corresponding characters):

Metric	Value
MLM Precision	89.54%
P2G Precision	97.88%

Citation

If this model contributes to your research, please cite it as follows:

@misc{proxectonos/PL-ModernBERT-gl,
  author       = {{Proxecto Nós}},
  title        = {{PL-ModernBERT-gl: Phoneme-level ModernBERT for Galician}},
  year         = {2026},
  publisher    = {Hugging Face},
  howpublished = {\url{[https://huggingface.co/proxectonos/PL-ModernBERT-gl](https://huggingface.co/proxectonos/PL-ModernBERT-gl)}},
}

Additional Information

Licensing

This model is licensed under the Apache License 2.0.

Authors and Credits

• Project Oversight: Proxecto Nós
• Technical Development: Gradiant (Centro Tecnolóxico de Telecomunicacións de Galicia)

Funding

This work is funded by the Ministerio para la Transformación Digital y de la Función Pública - Funded by EU – NextGenerationEU within the framework of the project Desarrollo de Modelos ALIA.

Acknowledgements

We would like to express our gratitude to the engineering and research teams at Gradiant for the technical development of this model.