The algorithm to analyze tonality and modulations in a piece of music

In algorithms module of musicpy, there are several algorithms implemented to analyze the tonality of a piece of music or a fragment of music.

The tonality here includes any custom scales defined in database module, including major, minor, all church modes, melodic minor, harmonic minor and so on, users can also customize new scales with pitch intervals.

There are totally 3 algorithms implemented for the goal at this time, each algorithm is stored in a function, respectively detect_scale, detect_scale2, detect_scale3. Among these 3 algorithms, the third algorithm has the ability to analyze tonality and modulations of a piece of music, the other 2 algorithms can only analyze the tonality of a piece of music.

Here we firstly introduce the third algorithm, which at this time is the most useful one in these 3 algorithms.

Usage

detect_scale3(current_chord,
              get_scales=False,
              most_appear_num=3,
              major_minor_preference=True,
              unit=5,
              key_accuracy_tol=0.9,
              is_chord=True)
  • current_chord: a chord instance to be analyzed
  • get_scales: if set to True, get the scale instances as result, if set to False, get a string represents the tonality and modulations as result
  • most_appear_num: number of the the most possible scales
  • major_minor_preference: put the major or minor key to the first in result
  • unit: the unit length in bars to analyze tonality and modulations
  • key_accuracy_tol: the minimum percentage of the ratio of notes matched with a scale to be determined as the scale in the analysis range
  • is_chord: if set to True, use the given chord instance directly to analyze, if set to False, merge the input as a list of chord instances to a chord instance and analyze

The output when get_scales is set to False is in the format [start1, end1] scale1, scale2, ..., [start2, end2] scale1, scale2, ..., [startn, endn] scale1, scale2, ..., each start and end is the bar range for each tonality that appears in the given input.

Examples

import musicpy as mp
current_piece = mp.read('test.mid')
current_chord, current_bpm, current_start_time = current_piece.merge()
current_scales = mp.alg.detect_scale3(current_chord)
>>> print(current_scales)
[0, 25] G major, E minor, [25, 44.25] G minor, A# major