pitchspelling.cpp

#include <vector>
#include <set>
#include <array>
#include <numeric>
#include <algorithm>
#include <iostream>
#include <math.h>

// Because C++ mod is really remainder not mod
int mod(int a, int b) { return a % b + b * (a < 0); }
int diatonic_to_chromatic(int d, int a = 0) { return d * 2 - (d / 7) * 2 - (mod(d, 7) > 2) + a; }

struct Note
{
	int pitch = 0, acc = 0;
	std::array<unsigned, 12> chromagram = {};

	int diatonic() { return (pitch - acc) / 2 + ((pitch - acc) / 12) + (mod((pitch - acc), 12) > 4); }
	void set_acc_by_diatonic(int step)
	{
		acc = mod(pitch, 12) - diatonic_to_chromatic(mod(step, 7));
		acc -= 12 * (acc > 6);
	}
};

void pitchSpell(std::vector<Note>& notes, int kPre = 10, int kPost = 42)
{
	for(int i = 0; i < notes.size(); i++)
		for(int j = std::max(0, i - kPre); j < std::min((int)notes.size(), i + kPost); j++)
			++notes[i].chromagram[notes[j].pitch % 12];

	std::array<int, 12> morphInt = {0, 1, 1, 2, 2, 3, 3, 4, 5, 5, 6, 6};
	std::array<int, 12> initMorph = {0, 1, 1, 2, 2, 3, 4, 4, 5, 5, 6, 6};
	int c0 = notes[0].pitch % 12;
	int m0 = initMorph[c0];
	std::array<int, 12> tonicMorphForTonicChroma;
	for(int ct = 0; ct < 12; ct++)
		tonicMorphForTonicChroma[ct] = mod(m0 - morphInt[mod(c0-ct, 12)], 7);

	for(auto& note : notes)
	{
		std::vector<std::set<int>> chromas(7);
		for(int ct = 0; ct < 12; ct++)
			chromas[mod(morphInt[mod(note.pitch % 12 - ct, 12)] + tonicMorphForTonicChroma[ct], 7)].insert(ct);

		int maxStrength = -1;
		int maxM = 0;
		for(int m = 0; m < 7; m++)
		{
			int strength = 0;
			for(int tonicChroma : chromas[m])
				strength += note.chromagram[tonicChroma];

			maxM = strength > maxStrength ? m : maxM;
			maxStrength = std::max(strength, maxStrength);
		}

		note.set_acc_by_diatonic(maxM);
		std::cout << note.pitch << " " << maxM << " " << note.acc << std::endl;
	}
}

int main(int argc, char** argv)
{
    std::vector<int> pitches = {0, 0, 7, 7, 9, 9, 7, 7, 5, 5, 4 ,4 ,3, 3, 0, 0};
	std::vector<Note> notes;
	for(auto p : pitches) notes.push_back({p, 0});
	pitchSpell(notes);
	for(auto n : notes)
	{
		std::cout << "CDEFGAB"[(n.diatonic() + 7*100) % 7] << "-b #+"[n.acc + 2] << ' ';
	}
	return 0;
}

Can you post some code that tests/demos this?

Sure you can do something like:

<Just added it above, because this view didn't work>

To just dump in some time ordered midi pitching and it will print back those pitches as note names + accidentals. I just did this and combined it with grep -Po "(?<=)\d+(?=)" to just get all pitches out of an imploded score, then you can do the same for the tpc values in the score and check the accuracy. It's all very hacky I apologize, just spend an hour or 2 on it to see the result.