amads.melody.contour.step_contour

Calculates the Step Contour of a melody, along with related features, as implemented in the FANTASTIC toolbox of Müllensiefen (2009) [1] (features 20–22). Exemplified in Steinbeck (1982) [2], Juhász (2000) [3], Eerola and Toiviainen (2004) [4].

class amads.melody.contour.step_contour.StepContour(pitches, durations, step_contour_length=64)

Class for calculating and analyzing the step contour of a melody. A step contour is a list of MIDI pitch values, repeated proportionally to the duration (measured in tatums) of each note relative to the total melody length. This list is normalized to a user defined length, defaulting to 64 steps as used in FANTASTIC. Rests are considered as extending the duration of the previous note.

Examples

>>> pitches = [60, 64, 67]  # C4, E4, G4
>>> durations = [2.0, 1.0, 1.0]  # First note is 2 beats, others are 1 beat
>>> sc = StepContour(pitches, durations)
>>> len(sc.contour)  # Default length is 64
64
>>> pitches = [60, 62, 64, 65, 67]  # C4, D4, E4, F4, G4
>>> durations = [1.0, 1.0, 1.0, 1.0, 1.0]  # Notes have equal durations
>>> sc = StepContour(pitches, durations)
>>> sc.contour[:8]  # First 8 values of 64-length contour
[60, 60, 60, 60, 60, 60, 60, 60]
>>> sc.global_variation  # Standard deviation of contour
2.3974
>>> sc.global_direction  # Correlation with ascending line
0.9746
>>> sc.local_variation  # Average absolute difference between adjacent values
0.1111

Parameters:

• pitches (list[int])

• durations (list[float])

• step_contour_length (int)

property global_direction: float

Calculate the global direction of the step contour by taking the correlation between the step contour vector and an ascending linear function y = x.

Returns:

Float value representing the global direction of the step contour Returns 0.0 if the contour is flat

Return type:

float

Examples

>>> sc = StepContour([60, 62, 64], [1.0, 1.0, 1.0])
>>> sc.global_direction
0.943
>>> sc = StepContour([60, 60, 60], [1.0, 1.0, 1.0])
>>> sc.global_direction
0.0
>>> sc = StepContour([64, 62, 60], [1.0, 1.0, 1.0])  # Descending melody
>>> sc.global_direction
-0.943

property global_variation: float

Calculate the global variation of the step contour by taking the standard deviation of the step contour vector.

Returns:

Float value representing the global variation of the step contour

Return type:

float

Examples

>>> sc = StepContour([60, 62, 64], [1.0, 1.0, 1.0])
>>> sc.global_variation
1.64

property local_variation: float

Calculate the local variation of the step contour, by taking the mean absolute difference between adjacent values.

Returns:

Float value representing the local variation of the step contour

Return type:

float

Examples

>>> sc = StepContour([60, 62, 64], [1.0, 1.0, 1.0])
>>> sc.local_variation
0.0634