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function y=synth(freq,dur,amp,Fs,type)
% y=synth(freq,dur,amp,Fs,type)
%
% Synthesize a single note
%
% Inputs:
% freq - frequency in Hz
% dur - duration in seconds
% amp - Amplitude in range [0,1]
% Fs - sampling frequency in Hz
% type - string to select synthesis type
% current options: 'fm', 'sine', or 'saw'
% Copyright (c) 2009 Ken Schutte
% more info at: http://www.kenschutte.com/midi
if nargin<5
error('Five arguments required for synth()');
end
N = floor(dur*Fs);
if N == 0
warning('Note with zero duration.');
y = [];
return;
elseif N < 0
warning('Note with negative duration. Skipping.');
y = [];
return;
end
n=0:N-1;
if (strcmp(type,'sine'))
y = amp.*sin(2*pi*n*freq/Fs);
elseif (strcmp(type,'saw'))
T = (1/freq)*Fs; % period in fractional samples
ramp = (0:(N-1))/T;
y = ramp-fix(ramp);
y = amp.*y;
y = y - mean(y);
elseif (strcmp(type,'fm'))
t = 0:(1/Fs):dur;
envel = interp1([0 dur/6 dur/3 dur/5 dur], [0 1 .75 .6 0], 0:(1/Fs):dur);
I_env = 5.*envel;
y = envel.*sin(2.*pi.*freq.*t + I_env.*sin(2.*pi.*freq.*t));
else
error('Unknown synthesis type');
end
% smooth edges w/ 10ms ramp
if (dur > .02)
L = 2*fix(.01*Fs)+1; % L odd
ramp = bartlett(L)'; % odd length
L = ceil(L/2);
y(1:L) = y(1:L) .* ramp(1:L);
y(end-L+1:end) = y(end-L+1:end) .* ramp(end-L+1:end);
end