Oh audioguru, thank you very much,
It makes sense somewhat now.
I would like to know more of Adding, Summing and or modulating signals now specially with your explanation. I made a search via internet but I did not find anything related to our discussion here. maybe I did not use the right keywords? Can somebody help me out for that please? Sorry my knowledge of waves interefernce is weak and I was not able to find a good resource to improve that.
Besides, what is the BEST way to add to signal together? An op-amp or adder or is there any special chip?
P.s. audioguru, When I was looking at the picture you have drown I thought what will happen if somebody Modulates that Added signal too?? What we will have on the output of the modulator?