Mauch MIREX 2010

function rootspelling = chordroot_spelling(key, root, degrees)

temp = strsplit(':', key);

keyroot = temp{1};

if length(temp) > 1

    keymode = temp{2};

else

    keymode = 'major';

end

% major scale

scale{1} = [0 2 4 5 7 9 11];

% harmonic minor scale

scale{2} = [0 2 3 5 7 8 11];

diatonic = {'C','D','E','F','G','A','B'};

keymode_number = find(strcmp({'major','minor'},keymode));

if ischar(root)

    rootdegree = find(strcmp(diatonic,root(1)));

    rootpc = scale{1}(strcmp(diatonic,root(1))) + length(strfind(root,'#')) - length(strfind(root,'b'));

else

    [rootdegree, rootdegree]= min(abs(scale{1}-root));

    rootpc = root;

end

deg = [];

pcs = [];

for ii = 1:length(degrees)

    deg = [deg mod(rootdegree + str2num(degrees{ii}(end)) - 2,7)+1];

    pcs = [pcs mod(rootpc + degree2semitone(degrees{ii}),12)];

end

keyrootpc = scale{1}(strcmp(diatonic,keyroot(1))) + length(strfind(keyroot,'#')) - length(strfind(keyroot,'b'));

keydegree = find(strcmp(diatonic,keyroot(1)));

scalesemitone = circshift(mod(scale{keymode_number} + keyrootpc,12),[0 keydegree-1]);

fit = [0 0 0];

for deviation = -1:1 % test if the best degree is lower, just right or higher

    currdeg = mod(deg+deviation-1,7) + 1;

    chordaccidentals = mod(scalesemitone(currdeg) - pcs + 12 + 6,12) - 6;

    fit(deviation+2) = sum(abs(chordaccidentals));

end

[bestfitval, bestfit] = min(fit);

bestrootdegree = mod(rootdegree + bestfit - 2 - 1,7) + 1;

bestrootaccidentals = mod(rootpc - scale{1}(bestrootdegree)+6,12)-6;

switch bestrootaccidentals

    case -2 

        suff = 'bb';

    case -1

        suff = 'b';

    case 0

        suff = '';

    case 2 

        suff = '##';

    case 1

        suff = '#';

end

rootspelling = [diatonic{bestrootdegree}, suff];