title: What Makes a Track Hard to Separate? Predicting HTDemucs Quality
subtitle: Audio feature correlation with separation SDR across 50 MUSDB18-7s tracks
run_date: March 14, 2026
run_timestamp: '2026-03-14T12:12:11'
model: htdemucs_ft
dataset: MUSDB18-7s
n_tracks: 50
vocal_sdr_range:
  min: -19.06
  max: 16.42
  median: 8.8
  std: 5.74
key_finding: The strongest predictor of vocal SDR is 'Chroma variance (harmonic complexity)'
  (r = 0.522). Tracks with higher harmonic-to-percussive ratio tend to separate more
  cleanly.
correlations:
- &id004
  feature: rms_energy
  feature_label: Overall loudness (RMS energy)
  stem: vocals
  pearson_r: -0.235
  n: 50
- feature: rms_energy
  feature_label: Overall loudness (RMS energy)
  stem: drums
  pearson_r: -0.133
  n: 50
- feature: rms_energy
  feature_label: Overall loudness (RMS energy)
  stem: bass
  pearson_r: 0.029
  n: 50
- feature: rms_energy
  feature_label: Overall loudness (RMS energy)
  stem: other
  pearson_r: -0.228
  n: 50
- feature: spectral_centroid_mean
  feature_label: Spectral brightness (centroid mean)
  stem: vocals
  pearson_r: -0.12
  n: 50
- feature: spectral_centroid_mean
  feature_label: Spectral brightness (centroid mean)
  stem: drums
  pearson_r: 0.09
  n: 50
- feature: spectral_centroid_mean
  feature_label: Spectral brightness (centroid mean)
  stem: bass
  pearson_r: -0.025
  n: 50
- feature: spectral_centroid_mean
  feature_label: Spectral brightness (centroid mean)
  stem: other
  pearson_r: -0.481
  n: 50
- &id002
  feature: spectral_flatness_mean
  feature_label: Spectral flatness (tonal vs noisy)
  stem: vocals
  pearson_r: -0.265
  n: 50
- feature: spectral_flatness_mean
  feature_label: Spectral flatness (tonal vs noisy)
  stem: drums
  pearson_r: 0.213
  n: 50
- feature: spectral_flatness_mean
  feature_label: Spectral flatness (tonal vs noisy)
  stem: bass
  pearson_r: -0.021
  n: 50
- feature: spectral_flatness_mean
  feature_label: Spectral flatness (tonal vs noisy)
  stem: other
  pearson_r: -0.408
  n: 50
- &id003
  feature: zcr_mean
  feature_label: Zero crossing rate (noisiness)
  stem: vocals
  pearson_r: -0.256
  n: 50
- feature: zcr_mean
  feature_label: Zero crossing rate (noisiness)
  stem: drums
  pearson_r: 0.153
  n: 50
- feature: zcr_mean
  feature_label: Zero crossing rate (noisiness)
  stem: bass
  pearson_r: -0.101
  n: 50
- feature: zcr_mean
  feature_label: Zero crossing rate (noisiness)
  stem: other
  pearson_r: -0.368
  n: 50
- feature: harmonic_energy
  feature_label: Harmonic energy
  stem: vocals
  pearson_r: -0.173
  n: 50
- feature: harmonic_energy
  feature_label: Harmonic energy
  stem: drums
  pearson_r: -0.221
  n: 50
- feature: harmonic_energy
  feature_label: Harmonic energy
  stem: bass
  pearson_r: 0.161
  n: 50
- feature: harmonic_energy
  feature_label: Harmonic energy
  stem: other
  pearson_r: -0.107
  n: 50
- feature: percussive_energy
  feature_label: Percussive energy
  stem: vocals
  pearson_r: -0.145
  n: 50
- feature: percussive_energy
  feature_label: Percussive energy
  stem: drums
  pearson_r: 0.191
  n: 50
- feature: percussive_energy
  feature_label: Percussive energy
  stem: bass
  pearson_r: -0.194
  n: 50
- feature: percussive_energy
  feature_label: Percussive energy
  stem: other
  pearson_r: -0.335
  n: 50
- feature: hp_ratio
  feature_label: Harmonic-to-percussive ratio
  stem: vocals
  pearson_r: -0.201
  n: 50
- feature: hp_ratio
  feature_label: Harmonic-to-percussive ratio
  stem: drums
  pearson_r: -0.205
  n: 50
- feature: hp_ratio
  feature_label: Harmonic-to-percussive ratio
  stem: bass
  pearson_r: 0.303
  n: 50
- feature: hp_ratio
  feature_label: Harmonic-to-percussive ratio
  stem: other
  pearson_r: 0.207
  n: 50
- feature: onset_density
  feature_label: Onset density (rhythmic activity)
  stem: vocals
  pearson_r: -0.181
  n: 50
- feature: onset_density
  feature_label: Onset density (rhythmic activity)
  stem: drums
  pearson_r: -0.08
  n: 50
- feature: onset_density
  feature_label: Onset density (rhythmic activity)
  stem: bass
  pearson_r: -0.333
  n: 50
- feature: onset_density
  feature_label: Onset density (rhythmic activity)
  stem: other
  pearson_r: -0.163
  n: 50
- &id001
  feature: chroma_variance
  feature_label: Chroma variance (harmonic complexity)
  stem: vocals
  pearson_r: 0.522
  n: 50
- feature: chroma_variance
  feature_label: Chroma variance (harmonic complexity)
  stem: drums
  pearson_r: 0.095
  n: 50
- feature: chroma_variance
  feature_label: Chroma variance (harmonic complexity)
  stem: bass
  pearson_r: 0.142
  n: 50
- feature: chroma_variance
  feature_label: Chroma variance (harmonic complexity)
  stem: other
  pearson_r: 0.175
  n: 50
- &id005
  feature: vocal_band_energy
  feature_label: Vocal band energy (200-3kHz)
  stem: vocals
  pearson_r: -0.221
  n: 50
- feature: vocal_band_energy
  feature_label: Vocal band energy (200-3kHz)
  stem: drums
  pearson_r: -0.28
  n: 50
- feature: vocal_band_energy
  feature_label: Vocal band energy (200-3kHz)
  stem: bass
  pearson_r: -0.119
  n: 50
- feature: vocal_band_energy
  feature_label: Vocal band energy (200-3kHz)
  stem: other
  pearson_r: 0.033
  n: 50
top_vocal_predictors:
- *id001
- *id002
- *id003
- *id004
- *id005