Mauch MIREX 2010

%

%DEGREES2QUALITY convert a degreelist to chord quality enumeration

% 

% [quality,success, errormessage] = degrees2quality(degreelist, {verbose})

% 

% Converts a list of degree strings to an integer value denoting the

% chord's quality. Quality values are from the enumeration:

%

% 0   Major

% 1   Minor

% 2   Diminished

% 3   Augmented

% 4   Suspended

%

% Success = 1 if symbols parsed correctly, 0 otherwise. 

%

% If optional argument 'verbose' is 1, function prints any errormessage to 

% the screen.

% 

% calls:    degrees2semitones

% 

% returns:  quality (integer)

%           success  (boolean)  

%           errormessage (string)

%

%

% Author: Christopher Harte,  August 2005

% 

% Copyright: Centre for Digital Music, Queen Mary University of London 2005 

%

% This file is part of the C4DM Chord Toolkit.  

%

% The C4DM Chord Toolkit is free software; you can redistribute it and/or 

% modify it under the terms of the GNU General Public License as published 

% by the Free Software Foundation; either version 2 of the License, or

% (at your option) any later version.

%

% The C4DM Chord Toolkit is distributed in the hope that it will be useful,

% but WITHOUT ANY WARRANTY; without even the implied warranty of

% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

% GNU General Public License for more details.

%

% You should have received a copy of the GNU General Public License

% along with the C4DM Toolkit; if not, write to the Free Software

% Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

%

function [quality,success,errormessage] = degrees2quality(degreelist,verbose)

quality = '';

errormessage = '';

if nargin < 2

    verbose = 0;

end

% define templates for the 5 different triad chords (four quality families

% plus suspension) - weights mean maj thirds will have more effect than min

% 3rds which in turn have more effect than 5ths and then 2nds and 4ths

templates = [[1,0,0,0,6,0,0,4,0,0,0,0]; ... % maj

             [1,0,0,5,0,0,0,4,0,0,0,0]; ... % min

             [1,0,0,5,0,0,4,0,0,0,0,0]; ... % dim

             [1,0,0,0,6,0,0,0,4,0,0,0]; ... % aug

             [1,0,2,0,0,2,0,4,0,0,0,0]];    % sus

% get the semitone equivalents of the degrees in the degree list             

[semitones,success,error] = degrees2semitones(degreelist);

indexa = 1;

% initialise a binary vector showing which semitones are present 

present = zeros(1,12);

while indexa <= 3 && indexa <= length(semitones) 

    % for each of the first three semitones in the list make its position a

    % one in the vector 'present' 

    if semitones(indexa) < 12

        present(semitones(indexa)+1) = 1;

    end

    indexa = indexa +1;

end

% multiply present by the templates matrix to give a vector of scores for

% the possible qualities

qvector = templates * present';

% find maximum value from the qualities vector

% this function benfits from the max function's picking of the first

% maximum value if there are several equal ones so is predisposed toward 

% major if the quality is not obvious from the input. (e.g. C:(1) returns major)  

[value,index] = max(qvector);

% take 1 from index to give correct enumeration

quality = index-1;

if(success==0) 

    errormessage = sprintf([error 'Error in degrees2quality: incorrect degree in list "' degreelist '"\n']);

    if verbose == 1

        fprintf(1, errormessage);

    end

end