function [y,fs]=tune(notes)
%  [y,fs]=tune(notes)
% produce a phrase of music (?),
% from a string of 'notes'
% (a row vector of integers 1<=note<=24)
	tones=[261.2,277.2,293.6,311.1,329.6,349.2,370,392,415.3,440,466.2,493.9];
	tones=[tones,2*tones];% two octaves of the notes
	%  [C,Db,D,Eb,E,F,F#,G,Ab,A,Bb,B,C,...]
	y=[];fs=4000;
	[M,K]=size(notes);
	s=[zeros(1,40),2*ones(1,100),ones(1,560),zeros(1,300)];
	b=1.0e-004 *[0.2915    0.8744    0.8744    0.2915];
	a=[1.0000   -2.8744    2.7565   -0.8819];
	envelope=filter(b,a,s);
	for k=1:min(K,16)
		if M>1          % M>1 means chords
			s=zeros(size(envelope));
			for m=1:M
				s=s+modulate(envelope,fs,tones(notes(m,k)));
            end
			y=[y,s];
        else		
			y=[y,modulate(envelope,fs,tones(notes(k)))];
        end	
    end
	sound(y,fs)