% program chordplay
% S. Scott Moor September 2006, modified April 2008
% This script illustrates several principles about creating music and 
% sound, particularly for developing chords. 
%
% EXERCISE 1: Create a Major chord
% Play this script as is by typing "chordplay" at the command
% line or simply push the "run" icon on the editor toolbar. 

% set up initial values: sampling rate, basic frequency
clear
sf = 20000;
f = 523.25;

% the ratio of frequencies for adjacent notes is the twelfth root of two
b = 2^(1/12);

% Look at the frequencies created: 
disp(['The first frequency is ',num2str(f)]) 
disp(['The second frequency is ' num2str(f*b^4)])
disp(['The third frequency is ', num2str(f*b^7)])

% Notes in a major chord are 4 and 7 half steps apart respectively
% these frequencies can be calculated as shown above.  

% 1.  What are the names for these three notes? 
% 2.  What advantage can you see to calculating them this way instead of just
%     typing in the frequencies? 
% 3.  How are the three note series combined into one series/chord?  
%     You will have to look later in this program to answer this question. 

% here we create the three notes for a major chord
first = makesquare2(f, sf, 1, 2);
third = makesquare2(f*b^4, sf, .8, 2);
fifth = makesquare2(f*b^7, sf, .6, 2);

% EXERCISE 2: Add a delay
% Uncomment the four lines at the end of this section, run the
% script again and notice the delays that result. Look over these lines and
% see how the delay is created.  

pad = zeros(1,5000);
first = [first, pad, pad];
third = [pad, third, pad];
fifth = [pad, pad, fifth];

% 4. How is the delay created? 
% 5. Why is the pad added at the end of the first note twice?
% 6. What are the dimensions of the chord array (the # of rows and columns)?
%    Use the size command or add a size column to your workspace window.

% here we combine the notes and divide by 3 so that the maximum series
% value does not exceed the sound card limit of 1.  
chord = (first + third + fifth)/3;

% EXERCISE 3: Play two notes in stereo
% You can also create multiple sounds by sending one to the right channel
% and one to the left channel. For this approach we can only use two
% notes.   To accomplish this we change our sound vectors from row to 
% column vectors and concatenate them together.  
% Uncomment the line below and rerun the script to try this variation.

% chord = [first', fifth'];

% If you play this on a computer with stereo speakers or with headphones,
% you should be able to hear the first not start in the left speaker and
% the pick up the fifth in the right speaker.  

% 7. Look at your workspace again.  What are the dimensions of the chord
%    array now?  


% % now we can play the chord with the sound command
sound(chord,sf)