Make fft conjugate symmetry without use 'Symmetry' option

The final music is liitle bit strange ? why is that !

[f1,Fs1] = audioread('m.wav');
y1 = fft(f1);
[f2,Fs2] = audioread('r.wav');
y2= fft(f2);
Starting_Location=400000;
y1(Starting_Location : Starting_Location + length(y2) - 1)=y2;
y1 = [y1;conj(y1(end:-1:2))];
r_music = ifft(y1);
sound(r_music,Fs1);