Answer: I'm always happy to discuss the nexus between alien visitations and music theory. The five musical tones in Close Encounters are, in solfege, Re, Mi, Do, Do, So, as below. The second Do is an octave below the first.
The five tones were chosen by composer John Williams after trying about 350 of the approximately 134,000 possible five-note combinations available in the 12-tone chromatic scale. He said the choice was arbitrary, but actually they are critical tones of the major scale (see below). I haven't watched this movie for a long while, but I believe the hand signals are the Curwen hand signs as illustrated for question 22, above. Learn the signs for Do, Re, Mi, and So, perform the second Do lower, around waist level, and you can communicate with aliens yourself, should the need arise.
I think that the inhabitants of a distant galaxy would recognize and appreciate a melody formed of the major or minor scales, because they are both derived from universal acoustic principles: a vibrating string in another galaxy will have the same harmonic partials as it does here (partials you'll find discussed in the appendix of Exploring Theory with Practica Musica), and among the first and most audible of those partials are Do, Do an octave higher, So, Mi, and Re - hey, those are the same ones John Williams chose! So maybe his choice wasn't as random as he implied in interviews. Counting repeats and not going any higher than the almost-inaudible 10th partial, he left out only the 7th one, which theorists traditionally have considered to be an odd duck in that it can't form a consonant interval with the others. In that sense the German scientist would be on the right track, at least, in claiming all music to be derived from these. But it might be better to go a little farther and include the tones derived by filling in the scale with the above tones mirrored on the other side of the main note: the opposite of Mi is La, the opposite of So is Fa. That much I think you could trust the aliens to know, but I'll bet they'd like Mozart too.
What I would like to hear is their own Mozart. They must have one.
