Haven't seen this movie in a long time. Just turned the movie on and it's toward the end where they are communicating with the aliens using the keyboard. Don't remember but in the movie do they ever explain what the significance of the tones were? Like did they mean something or was it just a test from the aliens to see if we recognize patterns or something?
It was "Smoke on the Water" one of the most universally recognized classic rock tunes.
If the aliens had any form of music, odds are they would almost certainly know how to play it.
It was a greeting. Passed to the chosen few, so when they met with them...they can say "what's up, yo."