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Merge pull request #59 from gabriel-diaz-ucsd/gdiaz-branch

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gabriel-diaz-ucsd 2021-12-11 09:42:03 -08:00 committed by GitHub
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function x = generate_lullaby(amplitude, frequency, phase, fs, duration, duty)
% Generates sine waves that play 'twinkle twinkle little star'
% by using the frequency parameter as the root note for the melody.
% Currently the duty and duration parameters are not used within the
% function as there is no need for the former and it is currently
% difficult to constrain the melody duration based on user input.
% A function such as this one could be useful as a demo for what a
% melody sounds like on a synthesizer, and could even find use
% in toys designed to help small children sleep.
% CONTRIBUTORS:
% generate_lullaby created by Gabriel Diaz
% DOCUMENTATION:
% phase shift is in number of periods
% fs is the sampling frequency: how many sample points per second
% duration is time in seconds
% duty is a number between 0 and 1
%NOTE: whatever's passed as the duration parameter doesn't get used at
%the moment, since it's currently difficult to sync every note in the
%melody to play in shorter duartions such that the entire song lasts about
%as long as 'duration'
duration = 0;
duty = 0; %duty also isn't used in this function
%current durations that the song will work with
note_duration = 0.4;
song_duration = note_duration * 48;
%frequency multiples for all notes in melody, assuming that frequency is
%the root note of this chord:
maj_second_freq = frequency * 1.125;
maj_third_freq = frequency * 1.25;
fourth_freq = frequency * 1.33;
fifth_freq = frequency * 1.5;
maj_sixth_freq = frequency * 1.7;
% initialize local variables from input arguments
n = fs * note_duration; % number of samples (length of matrix)
dt = 1 / fs; % sampling period: time between two sample points
t = [1:n].*dt - phase; %initialize time scale template
%sine waves for every note in 'frequency's' respective major scale:
first = amplitude * sin(2 * pi * frequency * t - phase);
second = amplitude * sin(2 * pi * maj_second_freq * t - phase);
third = amplitude * sin(2 * pi * maj_third_freq * t - phase);
fourth = amplitude * sin(2 * pi * fourth_freq * t - phase);
fifth = amplitude * sin(2 * pi * fifth_freq * t - phase);
sixth = amplitude * sin(2 * pi * maj_sixth_freq * t - phase);
%each one of the three melodies making up the song:
melody1 = [first,first,fifth,fifth,sixth,sixth,fifth,fifth]; %size 8 notes
melody2 = [fourth,fourth,third,third,second,second,first,first]; %size 8 notes
melody3 = [fifth,fifth,fourth,fourth,third,third,second,second]; %size 8 notes
% populate the matrix(total size is 44 notes wide, which means the song's
% duration must fit within the specified duration parameter
x = [melody1,melody2,melody3,melody3,melody1,melody2];
%For testing
%t = 0:dt:song_duration;
%t(n) = [];
%plot(t, x);
%sound(x, fs);
end