ivan@81: function y=synth(freq,dur,amp,Fs,type)
ivan@81: % y=synth(freq,dur,amp,Fs,type)
ivan@81: %
ivan@81: % Synthesize a single note
ivan@81: %
ivan@81: % Inputs:
ivan@81: %  freq - frequency in Hz
ivan@81: %  dur - duration in seconds
ivan@81: %  amp - Amplitude in range [0,1]
ivan@81: %  Fs -  sampling frequency in Hz
ivan@81: %  type - string to select synthesis type
ivan@81: %         current options: 'fm', 'sine', or 'saw'
ivan@81: 
ivan@81: % Copyright (c) 2009 Ken Schutte
ivan@81: % more info at: http://www.kenschutte.com/midi
ivan@81: 
ivan@81: if nargin<5
ivan@81:   error('Five arguments required for synth()');
ivan@81: end
ivan@81: 
ivan@81: N = floor(dur*Fs);
ivan@81: 
ivan@81: if N == 0
ivan@81:   warning('Note with zero duration.');
ivan@81:   y = [];
ivan@81:   return;
ivan@81: 
ivan@81: elseif N < 0
ivan@81:   warning('Note with negative duration. Skipping.');
ivan@81:   y = [];
ivan@81:   return;
ivan@81: end
ivan@81: 
ivan@81: n=0:N-1;
ivan@81: if (strcmp(type,'sine'))
ivan@81:   y = amp.*sin(2*pi*n*freq/Fs);
ivan@81: 
ivan@81: elseif (strcmp(type,'saw'))
ivan@81: 
ivan@81:   T = (1/freq)*Fs;     % period in fractional samples
ivan@81:   ramp = (0:(N-1))/T;
ivan@81:   y = ramp-fix(ramp);
ivan@81:   y = amp.*y;
ivan@81:   y = y - mean(y);
ivan@81: 
ivan@81: elseif (strcmp(type,'fm'))
ivan@81: 
ivan@81:   t = 0:(1/Fs):dur;
ivan@81:   envel = interp1([0 dur/6 dur/3 dur/5 dur], [0 1 .75 .6 0], 0:(1/Fs):dur);
ivan@81:   I_env = 5.*envel;
ivan@81:   y = envel.*sin(2.*pi.*freq.*t + I_env.*sin(2.*pi.*freq.*t));
ivan@81:   
ivan@81: else
ivan@81:   error('Unknown synthesis type');
ivan@81: end
ivan@81: 
ivan@81: % smooth edges w/ 10ms ramp
ivan@81: if (dur > .02)
ivan@81:   L = 2*fix(.01*Fs)+1;  % L odd
ivan@81:   ramp = bartlett(L)';  % odd length
ivan@81:   L = ceil(L/2);
ivan@81:   y(1:L) = y(1:L) .* ramp(1:L);
ivan@81:   y(end-L+1:end) = y(end-L+1:end) .* ramp(end-L+1:end);
ivan@81: end