christopherh@1: %
christopherh@1: %INTERVALS2QUALITY Return the quality of a given interval_list
christopherh@1: % 
christopherh@1: % [quality,success, errormessage] = intervals2quality(interval_list, {verbose})
christopherh@1: % 
christopherh@1: % Converts a list of interval strings to an integer value denoting the
christopherh@1: % chord's quality. Quality values are from the enumeration:
christopherh@1: %
christopherh@1: % 0   Major
christopherh@1: % 1   Minor
christopherh@1: % 2   Diminished
christopherh@1: % 3   Augmented
christopherh@1: % 4   Suspended
christopherh@1: %
christopherh@1: % Success = 1 if symbols parsed correctly, 0 otherwise. 
christopherh@1: %
christopherh@1: % If optional argument 'verbose' is 1, function prints any errormessage to 
christopherh@1: % the screen.
christopherh@1: % 
christopherh@1: % calls:    intervals2semitones
christopherh@1: % 
christopherh@1: % returns:  quality (integer)
christopherh@1: %           success  (boolean)  
christopherh@1: %           errormessage (string)
christopherh@1: %
christopherh@1: %
christopherh@1: % Author: Christopher Harte,  March 2009
christopherh@1: % 
christopherh@1: % Copyright: Centre for Digital Music, Queen Mary University of London 2005 
christopherh@1: %
christopherh@1: % This file is part of the C4DM Chord Toolkit V2.0  
christopherh@1: %
christopherh@1: % The C4DM Chord Toolkit is free software; you can redistribute it and/or 
christopherh@1: % modify it under the terms of the GNU General Public License as published 
christopherh@1: % by the Free Software Foundation; either version 2 of the License, or
christopherh@1: % (at your option) any later version.
christopherh@1: %
christopherh@1: % The C4DM Chord Toolkit is distributed in the hope that it will be useful,
christopherh@1: % but WITHOUT ANY WARRANTY; without even the implied warranty of
christopherh@1: % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
christopherh@1: % GNU General Public License for more details.
christopherh@1: %
christopherh@1: % You should have received a copy of the GNU General Public License
christopherh@1: % along with the C4DM Toolkit; if not, write to the Free Software
christopherh@1: % Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
christopherh@1: 
christopherh@1: %
christopherh@1: function [quality,success,errormessage] = intervals2quality(interval_list,verbose)
christopherh@1: 
christopherh@1: 
christopherh@1: 
christopherh@1: 
christopherh@1: quality = '';
christopherh@1: errormessage = '';
christopherh@1: 
christopherh@1: if nargin < 2
christopherh@1:     verbose = 0;
christopherh@1: end
christopherh@1: 
christopherh@1: % define templates for the 5 different triad chords (four quality families
christopherh@1: % plus suspension) - weights mean maj thirds will have more effect than min
christopherh@1: % 3rds which in turn have more effect than 5ths and then 2nds and 4ths
christopherh@1: 
christopherh@1: templates = [[1,0,0,0,6,0,0,4,0,0,0,0]; ... % maj
christopherh@1:              [1,0,0,5,0,0,0,4,0,0,0,0]; ... % min
christopherh@1:              [1,0,0,5,0,0,4,0,0,0,0,0]; ... % dim
christopherh@1:              [1,0,0,0,6,0,0,0,4,0,0,0]; ... % aug
christopherh@1:              [1,0,2,0,0,2,0,4,0,0,0,0]];    % sus
christopherh@1:              
christopherh@1:          
christopherh@1: % get the semitone equivalents of the intervals in the interval list             
christopherh@1: [semitones,success,error] = intervals2semitones(interval_list);
christopherh@1: 
christopherh@1: indexa = 1;
christopherh@1: 
christopherh@1: % initialise a binary vector showing which semitones are present 
christopherh@1: present = zeros(1,12);
christopherh@1: 
christopherh@1: while indexa <= 3 && indexa <= length(semitones) 
christopherh@1:     
christopherh@1:     % for each of the first three semitones in the list make its position a
christopherh@1:     % one in the vector 'present' 
christopherh@1:     
christopherh@1:     if semitones(indexa) < 12
christopherh@1:     
christopherh@1:         present(semitones(indexa)+1) = 1;
christopherh@1:     
christopherh@1:     end
christopherh@1:     indexa = indexa +1;
christopherh@1:     
christopherh@1: end
christopherh@1: 
christopherh@1: % multiply present by the templates matrix to give a vector of scores for
christopherh@1: % the possible qualities
christopherh@1: qvector = templates * present';
christopherh@1: 
christopherh@1: 
christopherh@1: % find maximum value from the qualities vector
christopherh@1: % this function benfits from the max function's picking of the first
christopherh@1: % maximum value if there are several equal ones so is predisposed toward 
christopherh@1: % major if the quality is not obvious from the input. (e.g. C:(1) returns major)  
christopherh@1: [value,index] = max(qvector);
christopherh@1: 
christopherh@1: % take 1 from index to give correct enumeration
christopherh@1: quality = index-1;
christopherh@1: 
christopherh@1: 
christopherh@1: if(success==0) 
christopherh@1: 
christopherh@1:     errormessage = sprintf([error 'Error in intervals2quality: incorrect interval in list "' interval_list '"\n']);
christopherh@1:     
christopherh@1:     if verbose == 1
christopherh@1:         fprintf(1, errormessage);
christopherh@1:     end
christopherh@1: end