samer@34: function y=shepardtone(N,C,prof,H)
samer@34: % shepardtone - Shepard tone by additive synthesis
samer@34: %
samer@34: % shepardtone ::
samer@34: %    N:natural    ~'size of buffers to produce',
samer@34: %    seq(real)    ~'sequence of chroma values, 0--1 is one octave',
samer@34: % -> seq([[1,N]]) ~'sum of components'.
samer@34: %
samer@34: % Note: the number of components must remain constant
samer@34: 
samer@34: if nargin<3, 
samer@34: 	prof=@(z)betapdf(2*z,2,9); 
samer@34: elseif isvector(prof),
samer@34: 	a=prof(1); b=prof(2);
samer@34: 	prof=@(z)betapdf(2*z,a,b);
samer@34: end
samer@34: 
samer@34: fc=0.25;
samer@34: if nargin<4, H=(-10:1)'; else H=H(:); end
samer@36: F=map(@(c)fc*2.^(H+mod(c,1)),C);  % frequencies
samer@36: A=map(prof,F); % component amplitudes
samer@34: y=addsynth(N,A,F,0);
samer@34: