fs=10000;
f0=261.63; 
f=[f0/2, f0, f0*2, f0*4];
t=[0:fs-1]/fs; % time for each note: 0.5 sec
x=[cos(2*pi*f(1)*t),cos(2*pi*f(2)*t),cos(2*pi*f(3)*t),cos(2*pi*f(4)*t)];
sound(x,fs)

