First contact. How would we go about this?

For the purpose of this thread, lets just pretend aliens dont communicate telepathicly. This is meant to be more of a fun discussion than an actual game plan.

I always found it funny in the movie close encounters how they played a sequence of lights and sounds to communicate with aliens. Now I havent actually seen the movie (I'd like to very much but I just cant find a copy of it ini this small town) so I dont understand the logic behind their lights and sounds. I always wondered though, how exactly would that convey a message, and what if the aliens perceive differently? We may play a soft tune with pretty bright colors and that may be a declaration of war to them... if it even makes any sense. I think if we were to play lights and sounds they'd just sit there and go wtf are they doing.... So if you were approached by an alien how would you make an attempt to show you're friendly and communicate.

[edit on 26-6-2005 by dez]

In Close Encounters they repeated the music that the craft was already known to play. It had something to do with mathematics.