Melody and Pitch

Pitch tracking follows the fundamental frequency of a sound over time. It is the backbone of melody extraction, vocal tuning checks, and transcription-style workflows.

Unlike chroma, which folds octaves away, pitch tracking keeps the exact frequency. This page expands the pitch section of MIR Overview.

Fundamental frequency (F0)

A pitched sound is not one frequency. It is a stack made from a fundamental frequency (F0) plus harmonics at integer multiples.

For example, when a singer holds A4, the F0 is 440 Hz. The recording also contains energy at 880 Hz, 1320 Hz, and other multiples.

The pitch you perceive corresponds to the F0. That is why pitch tracking is really F0 estimation over time. The hard part is deciding which peak is the fundamental and which peaks are harmonics.

YIN and pYIN

libsonare offers two related estimators:

• YIN finds F0 in the time domain using a difference function: it looks for the lag at which the waveform best repeats itself, then converts that period to frequency. It is accurate and cheap for clean monophonic audio.
• pYIN (probabilistic YIN) wraps YIN in a probabilistic model that tracks multiple F0 candidates over time and also estimates voicing — whether a frame is pitched at all. That makes it more robust on real recordings, where silences, breaths, and noise would otherwise produce spurious pitches.

Monophonic vs polyphonic

These estimators assume monophonic input: one note at a time, such as a solo voice, lead line, or bass.

They are not chord transcribers. If you feed them a full mix or a chord, the single-F0 assumption breaks down.

To track a melody inside a busy track, isolate the line first with a stem, HPSS, or source separation. Then run pitch tracking on the cleaner signal.

Voicing: when there is no pitch

Not every frame has a pitch. Rests, unvoiced consonants ("s", "t"), and percussion have no clear F0. A naive tracker will still report some number for these frames, producing a jumpy, meaningless line. Voicing detection, which pYIN is designed to provide, marks those frames as unpitched so the melody line has gaps where the music does.

PITCH · MELODY CONTOURIDLE

Pitch contour — tracing a melody as f0

NOTE

Pitch tracking estimates the fundamental frequency at every frame, turning a sung or played line into a contour you can see. The line breaks where the tracker hears no clear pitch. Toggle Smooth to watch the raw estimate — which jumps the odd octave at note attacks — settle into a clean melody once a median filter and octave correction are applied. Press play and the dot rides the pitch you hear.

Smooth

How libsonare tracks pitch

libsonare implements YIN and pYIN for F0 estimation on monophonic audio. analyzeMelody / MelodyAnalyzer uses frame-by-frame YIN frequency and confidence, then computes mean frequency, pitch range, stability, and a simple vibrato-rate estimate. Lower-level pitchYin / pitchPyin APIs expose YIN and pYIN tracks directly. Results can be converted to MIDI note numbers for tuning and editing workflows. Pitch tracking is most reliable on isolated, clearly pitched material and degrades on polyphonic or noisy mixes.

Related: Chroma Features, Mel, MFCC, and Timbre, Editing Basics, MIR Overview