midiano 26.5.16

Comprehensive Python package for MIDI music anomalies detection and features analysis

midiano

Comprehensive Python package for MIDI music anomalies detection and features analysis

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Installation

!pip install midiano

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Use as follows

Quick Start

from midiano import MIDIFeatureExtractor, MIDIProblemDetector

# Extract all features from a MIDI file
extractor = MIDIFeatureExtractor('song.mid')
features = extractor.extract_all()

# Detect concrete problems in the MIDI file
detector = MIDIProblemDetector(features)
problems = detector.detect()

# Print detected problems
for p in problems:
    print(f"[{p['severity'].upper()}] {p['category']}: {p['issue']} — {p['detail']}")

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Classes

MIDIFeatureExtractor

Extracts a comprehensive set of 200+ features from a MIDI file across 12 categories, designed for downstream anomaly detection and quality assessment.

from midiano import MIDIFeatureExtractor

# Basic usage
extractor = MIDIFeatureExtractor('song.mid')

# Filter to a specific MIDI channel (e.g., channel 0 only)
extractor = MIDIFeatureExtractor('song.mid', filter_channel=0)

# Extract all features as a flat dictionary
features = extractor.extract_all()

Constructor Parameters:

Parameter	Type	Default	Description
midi_filepath	str	required	Path to the MIDI file
filter_channel	int or None	None	If set, only extract notes from this MIDI channel

Key Properties:

Property	Type	Description
filename	str	Basename of the MIDI file
parse_error	str or None	Error message if parsing failed
notes	list	All note events sorted by (start, duration, pitch)
tempos	list	Tempo change events
time_sigs	list	Time signature events
key_sigs	list	Key signature events
patches	dict	Patch changes per track
control_changes	list	Control change events
pitch_bends	list	Pitch wheel events
ticks_per_quarter	int	Ticks per quarter note from the file header

Feature Categories

extract_all() returns a flat dictionary with features prefixed by category:

1. Structural / Metadata (struct_) File size, track count, note count, duration, tempo change count, time signature changes, empty track detection, note density, file efficiency.

features = MIDIFeatureExtractor('song.mid').extract_all()

features['struct_total_notes']           # Total number of notes
features['struct_track_count']           # Number of tracks
features['struct_duration_secs']         # Duration in seconds
features['struct_notes_per_second']      # Note density
features['struct_empty_track_ratio']     # Ratio of empty tracks
features['struct_nonstandard_tpq']       # 1 if ticks/quarter is unusual
features['struct_bytes_per_note']        # File size efficiency

2. Problem Detection (prob_) Zero-duration notes, velocity-zero notes, out-of-range pitches, negative durations, overlapping same-pitch notes, stuck notes, extreme bursts, tempo anomalies, excessive time-sig changes.

features['prob_zero_duration_ratio']         # Ratio of zero-duration notes
features['prob_velocity_zero_ratio']          # Ratio of velocity-zero notes
features['prob_out_of_range_pitch_count']     # Pitches outside 0–127
features['prob_negative_duration_count']      # Notes with negative duration
features['prob_overlapping_same_pitch_ratio'] # Overlapping same-pitch/channel
features['prob_stuck_note_ratio']             # Notes held >16 beats
features['prob_extreme_burst_count']          # Onsets with >20 simultaneous notes
features['prob_single_velocity']              # 1 if all notes share one velocity
features['prob_all_max_velocity']             # 1 if all notes at velocity 127

3. Instrument (instruments_) Unique instrument count, channel count, drum vs. melodic ratio, polytimbral flag, channel entropy.

features['instruments_unique_count']      # Distinct (channel, patch) pairs
features['instruments_channel_count']     # Active MIDI channels
features['instruments_drum_note_ratio']   # Ratio of channel-10 notes
features['instruments_is_polytimbral']    # 1 if multiple instruments
features['instruments_channel_entropy']   # Shannon entropy of channel distribution

4. Tempo & Pace (tempo_, pace_) BPM statistics (mean, std, min, max, range, median, IQR, skew, kurtosis, etc.), tempo change dynamics, notes per beat/bar.

features['tempo_bpm_mean']           # Average BPM
features['tempo_bpm_range']          # BPM max - min
features['tempo_bpm_change_max']     # Largest single tempo change
features['pace_notes_per_beat']      # Note density per beat
features['pace_notes_per_bar']       # Note density per bar

5. Grid & Rhythm (grid_) Quantization offset, start/duration alignment ratios, quarter/eighth/sixteenth note alignment, swing ratio, syncopation ratio, rhythmic entropy.

features['grid_start_alignment_ratio']   # How well notes snap to grid
features['grid_on_quarter_ratio']        # Quarter-note alignment
features['grid_on_eighth_ratio']         # Eighth-note alignment
features['grid_swing_ratio']             # Swing feel detection
features['grid_syncopation_ratio']       # Off-beat note ratio
features['grid_rhythmic_entropy']        # Rhythmic complexity

6. Harmonic & Key (harmonic_) Key estimation via Krumhansl-Schmuckler, key clarity/strength, pitch-class entropy, consonance/dissonance ratios, interval classification.

features['harmonic_key_tonic']           # Estimated key (0=C, 1=C#, …)
features['harmonic_key_is_minor']        # 1 if minor, 0 if major
features['harmonic_key_clarity']         # Correlation with key profile
features['harmonic_key_strength']        # Gap between top-2 key candidates
features['harmonic_pitch_class_entropy'] # High = atonal
features['harmonic_consonance_ratio']    # Consonant interval ratio
features['harmonic_dissonance_ratio']    # Dissonant interval ratio

7. Note (delta_times_, durations_, pitches_, velocities_, pitch_intervals_) Full statistical summaries (mean, std, min, max, range, median, Q25, Q75, IQR, skew, kurtosis, MAD, CV, entropy) for inter-onset intervals, durations, pitches, velocities, and melodic pitch intervals. Also includes pitch-class distribution, direction changes, step/leap ratios, and velocity dynamics.

features['durations_mean']               # Average note duration
features['pitches_range']                # Pitch span
features['pitch_intervals_mean']         # Average melodic interval
features['pitches_step_ratio']           # Ratio of steps (≤2 semitones)
features['pitches_leap_ratio']           # Ratio of leaps (>4 semitones)
features['pitches_ascending_ratio']      # Upward melodic motion ratio
features['delta_times_zero_ratio']       # Simultaneous onset ratio
features['delta_times_nonzero_mean']     # Avg non-zero inter-onset interval
features['pitch_class_0_ratio']          # C note ratio (0–11 for C–B)

8. Chord (chords_) Chord count, chord ratio, chord size statistics, uniqueness ratio, triad quality analysis (major, minor, diminished, augmented, sus2, sus4) — with correct inversion handling.

features['chords_count']            # Number of simultaneous note groups (≥2)
features['chords_ratio']            # Chord onsets / total onsets
features['chords_size_mean']        # Average notes per chord
features['chords_major_ratio']      # Major triad ratio
features['chords_minor_ratio']      # Minor triad ratio
features['chords_uniqueness_ratio'] # Harmonic variety

9. Polyphony (polyphony_) Max/mean polyphony (time-weighted), monophonic ratio, overlap ratio, multi-channel flag.

features['polyphony_max']                # Maximum simultaneous voices
features['polyphony_mean']               # Time-weighted average polyphony
features['polyphony_monophonic_ratio']   # Ratio of time with ≤1 voice
features['polyphony_overlap_ratio']      # Notes overlapping with others
features['polyphony_multi_channel']      # 1 if multiple channels used

10. Phrase (phrases_) Phrase segmentation via gap detection, phrase count, note count statistics, phrase length statistics.

features['phrases_count']            # Number of detected phrases
features['phrases_avg_note_count']   # Average notes per phrase
features['phrases_length_mean']      # Average phrase length in ticks

11. Dynamics (dynamics_) Velocity range, unique velocity count, dynamic range in dB, velocity entropy, consecutive same-velocity ratio, short-note ratio.

features['dynamics_velocity_range']       # Max velocity - min velocity
features['dynamics_range_db']             # Dynamic range in decibels
features['dynamics_entropy']              # Velocity distribution entropy
features['dynamics_same_consecutive_ratio']  # Flat dynamics indicator

12. Quality / Completeness (quality_) Presence of tempo/time-sig/key-sig metadata, default-value detection, sparsity/density flags, pitch range flags.

features['quality_has_tempo']           # 1 if tempo events exist
features['quality_has_time_sig']        # 1 if time signature exists
features['quality_default_tempo']       # 1 if tempo ≈ 120 BPM default
features['quality_default_time_sig']    # 1 if time sig is 4/4 default
features['quality_very_sparse']         # 1 if <0.5 notes/second
features['quality_very_dense']          # 1 if >100 notes/second
features['quality_very_narrow_range']   # 1 if pitch range <1 octave

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MIDIProblemDetector

Rule-based detector that identifies concrete MIDI problems — corruption, malformation, encoding errors, and quality issues — from extracted features.

from midiano import MIDIFeatureExtractor, MIDIProblemDetector

features = MIDIFeatureExtractor('song.mid').extract_all()
detector = MIDIProblemDetector(features)
problems = detector.detect()

Constructor Parameters:

Parameter	Type	Description
features	dict	Feature dictionary from MIDIFeatureExtractor.extract_all()

detect() Returns:

A list of problem dictionaries, each containing:

Key	Type	Description
category	str	'corruption', 'structure', or 'quality'
issue	str	Short problem identifier
severity	str	'critical', 'warning', or 'info'
detail	str	Human-readable description with values

Detected Problems:

Category	Issue	Severity Thresholds
corruption	parse_error	critical — file failed to parse
corruption	no_notes	critical — no note events found
corruption	zero_duration_notes	critical (>50%), warning (>10%), info (>1%)
corruption	velocity_zero_notes	critical (>30%), warning (>5%)
corruption	out_of_range_pitches	critical — any pitch outside 0–127
corruption	negative_durations	critical — any negative duration
corruption	overlapping_same_pitch	warning (>30%), info (>10%)
corruption	stuck_notes	warning — notes held >16 beats
corruption	extreme_burst	warning (>50), info (>20 simultaneous onsets)
structure	nonstandard_tpq	info — unusual ticks per quarter
structure	excessive_tempo_changes	warning (>10/s), info (>2/s)
structure	extreme_tempo	warning — BPM <20 or >300
structure	large_tempo_range	warning — >200 BPM variation
structure	excessive_time_sig_changes	warning — >10 time-sig changes
structure	many_empty_tracks	warning (>70%), info (>40%)
quality	no_dynamics	warning — single velocity value
quality	all_max_velocity	warning — all notes at velocity 127
quality	atonal	warning — key clarity <0.3
quality	weak_tonality	info — key clarity <0.5

# Filter by severity
critical = [p for p in problems if p['severity'] == 'critical']
warnings = [p for p in problems if p['severity'] == 'warning']

# Filter by category
corruption = [p for p in problems if p['category'] == 'corruption']

# Pretty-print all problems
for p in problems:
    icon = {'critical': '🔴', 'warning': '🟡', 'info': '🔵'}[p['severity']]
    print(f"{icon} [{p['severity'].upper()}] {p['issue']}: {p['detail']}")

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Batch Processing

from midiano import MIDIFeatureExtractor, MIDIProblemDetector
import os, json

midi_dir = 'path/to/midi/files'
results = []

for fname in tqdm.tqdm(os.listdir(midi_dir)):
    if not fname.endswith(('.mid', '.midi')):
        continue
    path = os.path.join(midi_dir, fname)
    
    extractor = MIDIFeatureExtractor(path)
    features = extractor.extract_all()
    
    if 'error' not in features:
        detector = MIDIProblemDetector(features)
        problems = detector.detect()
        features['problem_count'] = len(problems)
        features['critical_count'] = sum(1 for p in problems if p['severity'] == 'critical')
    
    results.append(features)

# Save features as JSON
with open('features.json', 'w') as f:
    json.dump(results, f, indent=2, default=str)

Anomaly Detection with Isolation Forest

import pandas as pd
from sklearn.ensemble import IsolationForest
from sklearn.preprocessing import StandardScaler
from midiano import MIDIFeatureExtractor

# Collect features from multiple MIDI files
feature_dicts = []
for path in midi_file_paths:
    f = MIDIFeatureExtractor(path).extract_all()
    if 'error' not in f:
        feature_dicts.append(f)

# Convert to DataFrame and clean
df = pd.DataFrame(feature_dicts).set_index('filename')
df = df.dropna(axis=1, how='any')          # drop columns with NaN
df = df.select_dtypes(include='number')     # keep only numeric columns

# Scale and detect anomalies
scaler = StandardScaler()
X = scaler.fit_transform(df)

iso = IsolationForest(contamination=0.1, random_state=42)
df['anomaly'] = iso.fit_predict(X)  # -1 = anomaly, 1 = normal

# Show flagged files
anomalies = df[df['anomaly'] == -1]
print(f"Flagged {len(anomalies)} anomalous MIDI files:")
print(anomalies.index.tolist())

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Attribution

• midiano was passionately vibe-coded with Z AI
• Artwork is a courtesy of Microsoft Copilot

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Project Los Angeles

Tegridy Code 2026