Singing Voice Synthesis Pitch Accuracy and Naturalness Statistics (2026): 55+ Data Points on Pitch Error, MOS Gaps, and Training Data

Singing voice synthesis pitch accuracy statistics 2026: the best models score 3.70 to 4.01 MOS vs 4.30 to 4.54 for human recordings in 5 benchmark papers.

The best singing voice synthesis model trained on the Opencpop corpus scored 3.70 on a 5-point mean opinion score (MOS) scale, while the professional singer’s own recordings scored 4.51 (Wang et al., Opencpop paper, Interspeech 2022). In four other benchmark papers the best model landed between 3.81 and 4.01, against 4.30 to 4.54 for real recordings (see section 4). Humans are not perfect either: 24 adults singing Happy Birthday from memory missed their target notes by a median of 19 cents, about a fifth of a semitone (Mauch, Frieler and Dixon, JASA 2014), and the median listener only detects a mistuned vocal at around 55 cents (Larrouy-Maestri, Harrison and Müllensiefen, Behavior Research Methods 2019). Speech synthesis has reached parity on several benchmarks, as our synthetic speech MOS statistics roundup shows, but singing has not. We aggregated data from the Opencpop, M4Singer, GTSinger and ACE-Opencpop corpus papers, the Singing Voice Conversion Challenges of 2023 and 2025, the SVDD 2024 deepfake detection challenge, the SingMOS-Pro rating benchmark, and peer-reviewed singing research in JASA, Frontiers in Psychology, PLoS One and the Journal of Research in Music Education.

TL;DR

  • The best Opencpop baseline scored 3.70 MOS vs 4.51 for the original recordings (Wang et al., Opencpop paper, Interspeech 2022).
  • 24 adult singers hit notes with a median error of 19 cents (Mauch, Frieler and Dixon, JASA 2014).
  • 28% of 50 occasional singers were classed as poor-pitch singers (Berkowska and Dalla Bella, Frontiers in Psychology 2013).
  • Only 37% of 1,046 people were accurate pitch matchers under a strict 50-cent rule (Pfordresher and Demorest, JRME 2021).
  • The median listener detects mistuning at a 54.989-cent shift (Larrouy-Maestri, Harrison and Müllensiefen, Behavior Research Methods 2019).
  • Giving DiffSinger the real singer’s pitch curve lifted prosody MOS from 3.72 to 4.02, but audio quality only from 3.92 to 3.97 (Zhang et al., M4Singer, NeurIPS 2022).
  • VISinger 2 fell from 3.96 to 3.02 MOS without its DSP synthesizer (Zhang et al., VISinger 2 paper 2022).
  • CoMelSinger came within 0.24 naturalness points of recordings for unseen singers (Zhao et al., CoMelSinger 2026).
  • ACE-Opencpop adds 128.9 hours of synthesized singing from 30 voices (Shi et al., ACE-Opencpop paper 2024).
  • No system reached human-level naturalness in SVCC 2025, with top systems near 3.7 vs about 3.9 for real singing (SVCC 2025 analysis paper).
  • SingMOS-Pro collected 44,247 quality ratings from 78 annotators (SingMOS-Pro benchmark paper 2026).
  • The best SVDD 2024 detector reached a 1.65% equal error rate (Zhang et al., SVDD 2024 challenge paper).

1. The Human Baseline: How Accurately People Really Sing

Pitch accuracy is measured in cents: 100 cents equal one semitone, the step between two neighbouring piano keys. A median note error of 19 cents across 24 unaccompanied singers (Mauch, Frieler and Dixon, JASA 2014) is the realistic target for a synthetic singer, not zero. Even trained voices stray: professionals became less exact on intervals, not more, when they switched to operatic technique.

The spread across the population is wide. Only 24% of untrained participants were accurate pitch matchers in the same dataset where 37% of the full sample were (Pfordresher and Demorest, JRME 2021). Tempo explains much of the difference: in a classic study of 62 occasional singers, most of the 15 nonmusicians retested at a slower tempo matched professional accuracy, and only two kept making many pitch errors (Dalla Bella, Giguère and Peretz, JASA 2007).

MetricValueSource
Median note error, 24 adults singing Happy Birthday without accompaniment19 centsMauch, Frieler and Dixon, JASA 2014
Median absolute pitch drift over a roughly 50-second performance11 centsMauch, Frieler and Dixon, JASA 2014
Mean interval deviation, 14 professional singers singing without operatic technique32.81 centsLarrouy-Maestri and Morsomme, Logopedics Phoniatrics Vocology 2014
Mean interval deviation, 63 occasional singers with no formal training50.83 centsLarrouy-Maestri and Morsomme, Logopedics Phoniatrics Vocology 2014
Mean interval deviation, the same professionals using operatic (lyrical) technique62.13 centsLarrouy-Maestri and Morsomme, Logopedics Phoniatrics Vocology 2014
Occasional singers classed as poor-pitch singers (2 standard deviations from group mean)28% (14 of 50)Berkowska and Dalla Bella, Frontiers in Psychology 2013
Accurate pitch matchers (90% or more of notes within 50 cents), combined sample of 1,04637%Pfordresher and Demorest, JRME 2021
Singing classified as accurate when the criterion is loosened to 100 cents94%Pfordresher and Demorest, JRME 2021

Most recent available data: Pfordresher and Demorest, Journal of Research in Music Education 2021. The poor-pitch share swings with the cut-off: on single sung pitches, 6% of the same 50 occasional singers fell beyond the 2 SD line but 58% fell beyond 50 cents, so any headline prevalence figure is only as good as its threshold.

2. Listener Tolerance: How Much Pitch Error Ears Forgive

Synthetic singers do not need to beat a tuner, they need to beat a listener. The median listener’s mistuning-detection ability matched a vocal pitch shift of 54.989 cents in the 333-person calibration of the Mistuning Perception Test, with 95% of listeners between 36.309 and 82.589 cents (Larrouy-Maestri, Harrison and Müllensiefen, Behavior Research Methods 2019). That is roughly half a semitone, well above the 19-cent median note error in section 1, although the two tests measure different things.

Ordinary listeners still judge pitch consistently. Lay judges’ scores tracked measured interval deviation almost as tightly as experts’ did, and they were stricter overall (Larrouy-Maestri et al., PLoS One 2015). For a synthesis model, that means a casual audience is a valid test panel for pitch errors, not just a panel of vocal coaches.

MetricValueSource
Detection threshold, low vs high musical training (Gold-MSI training score 10 vs 40)65.173 vs 43.219 centsLarrouy-Maestri, Harrison and Müllensiefen, Behavior Research Methods 2019
Correct mistuning detection, smallest vs largest shift tested (10 to 100 cents, chance = 50%)51.2% to 81.5%Larrouy-Maestri, Harrison and Müllensiefen, Behavior Research Methods 2019
Correlation with measured interval deviation: 3 expert judges vs lay judgesabout .83 vs about .79Larrouy-Maestri et al., PLoS One 2015
Mean interval deviation across 166 Happy Birthday performances rated55.97 cents (range 10.10 to 383)Larrouy-Maestri et al., PLoS One 2015
Correlation between pitch discrimination and pitch matching, 632 volunteersr(630) = -.31, p < .001Pfordresher and Demorest, JRME 2021

Most recent available data: Larrouy-Maestri, Harrison and Müllensiefen, 2019. The test shifted the whole vocal track by a constant amount, so it measures tolerance to a singer who is out of tune throughout, not to errors that vary from note to note, which the authors leave for future work.

3. Objective Pitch Metrics: What SVS Papers Measure

Singing voice synthesis (SVS) papers score pitch with F0 RMSE, the root mean square error between the generated and the real fundamental frequency (F0, the pitch curve). None of the SVS papers we reviewed reported that error in cents: the Opencpop, VISinger 2 and CSSinger tables give no unit at all, and ACE-Opencpop uses a logarithmic F0 scale. Human studies use cents, so a clean “machine vs human” pitch score does not exist yet.

What the numbers do show is ranking within a benchmark. On Opencpop, a Conformer model cut F0 RMSE from 29.99 to 26.72 compared with a Transformer baseline (Wang et al., Opencpop paper, Interspeech 2022), and VISinger 2 reached 26.0 with 25.7M parameters against CpopSing’s 137.5M (Zhang et al., VISinger 2 paper 2022). Semitone accuracy, reported as a percentage, is the closest metric to a human-style score, although the ACE-Opencpop paper does not spell out its formula.

MetricValueSource
F0 RMSE on the Opencpop test set, Transformer vs Conformer baseline (unit not stated)29.99 vs 26.72Wang et al., Opencpop paper, Interspeech 2022
F0 correlation with the real singer, Opencpop baselines0.893 to 0.904Wang et al., Opencpop paper, Interspeech 2022
F0 RMSE at 22 kHz: VISinger 2 vs VISinger vs CpopSing26.0 vs 33.7 vs 28.5Zhang et al., VISinger 2 paper 2022
Model size: VISinger 2 vs CpopSing25.7M vs 137.5M parametersZhang et al., VISinger 2 paper 2022
Semitone accuracy of VISinger2: Mandarin ACE-Opencpop vs Japanese Kiritan corpus65.19% vs 49.33%Shi et al., ACE-Opencpop paper 2024
F0 RMSE, F0 correlation and voiced/unvoiced error of CSSinger-FS on Opencpop28.601, 0.919 and 0.107Cui et al., CSSinger 2024
F0 RMSE on ACE-Opencpop: speech-language-model SVS vs TokSing vs XiaoiceSing62.79 vs 55.83 vs 71.67Zhao et al., speech language model SVS paper 2025

Voiced/unvoiced error tracks how often a model confuses voiced sound (the vocal folds vibrate, so a pitch exists) with unvoiced sound. The spread from 49.33% to 65.19% semitone accuracy for the same architecture suggests the score depends heavily on the corpus, so results from different corpora cannot be ranked against each other.

4. Naturalness: The MOS Gap Between Synthetic and Real Singing

MOS is the average rating that a listening panel gives on a 1 to 5 scale, and every paper here tested real recordings alongside the models. Across five benchmark papers the gap between the best model and real singing ranged from 0.45 to 0.81 MOS points (4.30 minus 3.85 on PopCS, 4.51 minus 3.70 on Opencpop). Speech synthesis has reported parity with recordings on several benchmarks; singing still trails by roughly half a point or more.

The newest zero-shot work narrows it. Zero-shot means the model sings in a voice it never heard during training. CoMelSinger, revised in April 2026, came within 0.24 naturalness points of real recordings for singers it had never heard (4.35 minus 4.11), the smallest gap in this set (Zhao et al., CoMelSinger 2026). Panels are small, though, often 10 to 20 listeners, so a 0.1-point lead is rarely decisive.

MetricValueSource
MOS on Opencpop: best baseline (CpopSing) vs recordings3.70 vs 4.51Wang et al., Opencpop paper, Interspeech 2022
MOS on PopCS: DiffSinger vs recordings3.85 vs 4.30Liu et al., DiffSinger, AAAI 2022
Audio quality MOS on M4Singer: DiffSinger vs recordings3.92 vs 4.52Zhang et al., M4Singer, NeurIPS 2022
MOS at 44.1 kHz: VISinger 2 vs recordings3.81 vs 4.32Zhang et al., VISinger 2 paper 2022
Audio quality MOS on GTSinger: StyleSinger vs recordings4.01 vs 4.54Zhang et al., GTSinger, NeurIPS 2024
Naturalness MOS, singers seen in training: CoMelSinger vs recordings4.02 vs 4.38Zhao et al., CoMelSinger 2026
Naturalness MOS, unseen singers (zero-shot): CoMelSinger vs recordings4.11 vs 4.35Zhao et al., CoMelSinger 2026

Most recent available data for those corpora: the Opencpop, PopCS, M4Singer and VISinger 2 rows date from 2022, so they mark the baseline for each corpus, not the current state of the art. Wider adoption figures for AI music tools sit in our AI music generation statistics.

5. Where Pitch Matters: What Changes When the Model Gets F0 Right

The cleanest test hands the model the real singer’s pitch curve and measures what improves. When DiffSinger received the real F0, its prosody MOS rose by 0.30 points (3.72 to 4.02) while audio quality rose by only 0.05 (3.92 to 3.97) (Zhang et al., M4Singer, NeurIPS 2022). Prosody here means the coherence and naturalness of the melodic delivery. Better pitch closes part of that gap, but even with the real F0 both scores stay below the recordings (4.47 and 4.52), so pitch is one limit among several.

Dynamic techniques are the hardest. In the Singing Voice Conversion Challenge 2025, a conversion task rather than score-based synthesis, the styles the organizers describe as having strong dynamic components (breathy, glissando, vibrato) scored the lowest style accuracy, while mostly static ones such as falsetto scored the highest (SVCC 2025 analysis paper).

MetricValueSource
F0 mean absolute error and voiced/unvoiced accuracy, DiffSinger predicted vs real F08.9990 vs 1.7061; 0.9406 vs 0.9856Zhang et al., M4Singer, NeurIPS 2022
VISinger 2 MOS, full model vs without the DSP synthesizer3.96 vs 3.02Zhang et al., VISinger 2 paper 2022
VISinger 2 MOS without the auxiliary mel-spectrum module3.85Zhang et al., VISinger 2 paper 2022
SVCC 2025 style accuracy: breathy, glissando, vibrato37.3%, 42.6%, 43.9%SVCC 2025 analysis paper
SVCC 2025 style accuracy: pharyngeal, mixed voice, falsetto44.8%, 48.3%, 48.8%SVCC 2025 analysis paper

The Opencpop authors reported that their baselines showed limited capability with rare pitches in the long tail of the training distribution, a limit that a single-singer corpus makes hard to escape.

6. Training Data: Hours of Singing Behind the Models

Singing models still learn from single- or double-digit hours of recorded singing. The Opencpop corpus that anchors much of the Mandarin SVS literature holds about 5.2 hours of singing from one professional female singer (Wang et al., Opencpop paper, Interspeech 2022). Recorded corpora such as Opencpop and M4Singer need note boundaries and musical scores annotated by hand, which is why real singing data grows slowly.

The workaround is synthetic data. ACE-Opencpop is derived from the Opencpop scores and synthesized with the ACE Studio singing synthesizer plus manual tuning of pitch contours, breaths and vibrato, producing 128.9 hours, and pre-training on it nudged VISinger2’s semitone accuracy on real Opencpop from 64.50% to 65.18% (Shi et al., ACE-Opencpop paper 2024). Pre-training on the real M4Singer corpus instead lowered it to 60.54%. ACE-Opencpop shares its songs with the target corpus, so this result says more about matching the target than about hours alone.

MetricValueSource
Opencpop: 1 professional singer, 100 songsabout 5.2 hours, 3,756 utterancesWang et al., Opencpop paper, Interspeech 2022
M4Singer: 20 professional singers (10 male, 10 female), 700 songs29.77 hours, 20,942 utterancesZhang et al., M4Singer, NeurIPS 2022
GTSinger: 20 professional singers, 9 languages, 6 techniques80.59 hours singing plus 16.16 hours paired speechZhang et al., GTSinger, NeurIPS 2024
ACE-Opencpop and ACE-KiSing synthesized corpora128.9 hours (30 voices) and 32.5 hours (34 voices)Shi et al., ACE-Opencpop paper 2024
VISinger2 semitone accuracy on Opencpop: no pre-training vs ACE-Opencpop vs M4Singer pre-training64.50% vs 65.18% vs 60.54%Shi et al., ACE-Opencpop paper 2024
VISinger2 on KiSing, trained alone vs with ACE-KiSing added: semitone accuracy and MOS68.12% to 72.51%; 3.58 to 3.83Shi et al., ACE-Opencpop paper 2024
Real singing pooled from 8 public corpora for the CtrSVDD benchmark47.64 hoursZang et al., CtrSVDD 2024

GTSinger’s nine languages are Chinese, English, Japanese, Korean, Russian, Spanish, French, German and Italian, and its six labelled techniques are mixed voice, falsetto, breathy, pharyngeal, vibrato and glissando, the same six styles scored in section 5.

7. Evaluation Methods and Benchmarks: How the Scores Are Produced

Small listening panels are the norm. Opencpop used 20 listeners per clip, the VISinger 2 test used ten listeners on 30 segments, and the ACE-Opencpop test used 30 listeners on 30 samples per system. Opencpop recordings scored 4.22 MOS in one test and 4.77 in another inside a single 2024 paper (Cui et al., CSSinger 2024), a 0.55-point swing larger than many of the gaps between models.

Automatic raters help at the system level but not per clip. The best MOS predictor on SingMOS-Pro reached a linear correlation of 0.88 when ranking systems, but only 0.58 on individual clips (SingMOS-Pro benchmark paper 2026). Detection is further along: on controlled data the top SVDD 2024 team cut equal error rate to 1.65% (Zhang et al., SVDD 2024 challenge paper), a topic covered in our audio deepfake forensics statistics.

MetricValueSource
SingMOS-Pro size7,981 clips, 44,247 ratings, 78 annotators, 11.15 hoursSingMOS-Pro benchmark paper 2026
Systems rated in SingMOS-Pro (synthesis, conversion, resynthesis, ground truth)141 (60, 17, 52 and 12)SingMOS-Pro benchmark paper 2026
Best automatic MOS predictor, linear correlation at system level vs clip level0.88 vs 0.58SingMOS-Pro benchmark paper 2026
SVCC 2023 submissions and listeners26 submissions (incl. 2 baselines); 40 English and 319 Japanese listenersHuang et al., SVCC 2023 paper
Spearman correlation of the UTMOS predictor with SVCC 2023 naturalness MOS (Task 1, Japanese listeners)0.77Huang et al., SVCC 2023 paper
SVCC 2025 naturalness, top systems vs real singingabout 3.7 vs about 3.9SVCC 2025 analysis paper
CtrSVDD real vs deepfake singing, 14 generation methods, 164 singer identities47.64 vs 260.34 hoursZang et al., CtrSVDD 2024
SVDD 2024 equal error rate: top team vs baselines; teams beating both baselines1.65% vs 11.16% and 12.03%; 37 of 47Zhang et al., SVDD 2024 challenge paper

Context: in SVCC 2023 the top systems in both tasks were judged not significantly different from natural samples on naturalness, while in SVCC 2025, which scored singing style as well, no system reached human-level naturalness. The analysis concludes that modeling singing style still remains a challenge.

Summary: Singing Voice Synthesis Pitch Accuracy and Naturalness by the Numbers

MetricValueSource
Median note error, 24 unaccompanied adult singers19 centsMauch, Frieler and Dixon, JASA 2014
Accurate pitch matchers in a sample of 1,04637%Pfordresher and Demorest, JRME 2021
Singing classified as accurate under a looser 100-cent criterion94%Pfordresher and Demorest, JRME 2021
Poor-pitch occasional singers (2 SD criterion)28% (14 of 50)Berkowska and Dalla Bella, Frontiers in Psychology 2013
Pitch shift matching the median listener’s detection ability54.989 centsLarrouy-Maestri, Harrison and Müllensiefen, Behavior Research Methods 2019
Best Opencpop baseline vs recordings, MOS3.70 vs 4.51Wang et al., Opencpop paper, Interspeech 2022
VISinger 2 vs recordings at 44.1 kHz, MOS3.81 vs 4.32Zhang et al., VISinger 2 paper 2022
CoMelSinger vs recordings, naturalness MOS for unseen singers4.11 vs 4.35Zhao et al., CoMelSinger 2026
Prosody MOS gain vs audio quality MOS gain from real F0 (DiffSinger)+0.30 vs +0.05Zhang et al., M4Singer, NeurIPS 2022
VISinger 2 MOS without its DSP synthesizer3.02 (vs 3.96)Zhang et al., VISinger 2 paper 2022
VISinger2 semitone accuracy, ACE-Opencpop vs Kiritan65.19% vs 49.33%Shi et al., ACE-Opencpop paper 2024
SVCC 2025 style accuracy for vibrato43.9%SVCC 2025 analysis paper
GTSinger corpus size80.59 hours, 20 singers, 9 languagesZhang et al., GTSinger, NeurIPS 2024
ACE-Opencpop synthesized corpus size128.9 hours, 30 voicesShi et al., ACE-Opencpop paper 2024
Opencpop recordings scored in two separate tests within one paper, MOS4.22 vs 4.77Cui et al., CSSinger 2024
SingMOS-Pro ratings collected44,247 from 78 annotatorsSingMOS-Pro benchmark paper 2026
SVDD 2024 top equal error rate1.65%Zhang et al., SVDD 2024 challenge paper

Methodology and Sources

Last updated: October 31, 2026. We update this roundup quarterly, and the next refresh is expected when the ICASSP 2027 proceedings and the next Singing Voice Conversion Challenge results are published.

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