The Voyager Gold Record (now being overcelebrated for its Nth anniversary) attached to a spacecraft is a bit incongruous. Not because of the somewhat tweeness of it – I think all spacecraft not destined to be crashed into a planet or sun ought to have some artistic/sociological document stuck to the side. It’s just the arcaneness of the method – an analog groove designed to be played by a needle spinning at a certain speed.
Music played in such a manner has a longer span than anything else. Clearly you can still buy vinyl if you have the correct facial hair and head covering. It goes from Edison wax cylinders to 200g pressed virgin vinyl. As a medium for communication with actual space aliens, it seems archaic. Though I can’t think of a better one, and neither can anyone else. Encoding a signal via ones and zeros via some long-lasting method (kinks in wire, pits in a gold disc, etc.)?
Not that I’m not sure that playing sounds via the transduction of electrical signals from modulated grooves in a soft medium will not outlast any digital signal. If you want your writing to last, scratch it on clay and bake it. If you want your photographs to be seen by your heirs, put them on paper. Maybe if you want your music to last for the ages, engrave it on vinyl.
Our planet broadcast signals into space for about 50 years – roughly from WW2, the Big One, to the advent of the cell phone. Now everything broadcast is digitally modulated spread spectrum pseudorandom low power signals. All the over-the-air communications of our civilization looks like noise. The rest is traveling down fibers emitting nothing. A few leaks from where the two meet.
Aliens paying attention would have seen this solar system glow faintly at a few tens or hundreds of MHz for a few decades then sink back into radio silence with a slightly higher background level.
Aliens discovering the Voyager record would likely marvel at the analogue-ness of it! Digital seems inevitable in any imaginable civilization, but we sent out this analog thing that it’s easy to imagine no other civilization would ever reproduce. Largely I think as a function of the transitional era in which the Voyagers were created. On the cusp of the transition between analog and digital, carrier waves and spread spectrum, between Carl Sagan and Amerika becoming Nazi.