Forty years ago today, NASA launched the space probe Voyager 2 — it’s currently a little less than 11 billion miles away from Earth — and a couple weeks later it was followed by Voyager 1, which has surpassed its twin and is now around 13 billion miles away. Both spacecrafts contain a 12-inch, gold-plated copper phonograph record that features messages from our planet. The record has some more scientific stuff on it that you’d probably expect — recordings of the sounds of Earth (volcanoes, earthquakes, thunder, wind, rain, etc.), greetings in 55 languages, whale sounds — but it also has a lot of music included as well.

Getting the phonograph records put on board of each Voyager was largely the work of Carl Sagan, who ironically ended up not even getting to keep a copy of it for himself. (Only 12 copies of it were ever pressed. There was a recent Kickstarter campaign to reissue the record. It’s now available to pre-order.)

The music selections were, for the most part, curated by Sagan’s friend Timothy Ferris. Rock ‘n roll is represented entirely by Chuck Berry’s “Johnny B. Goode,” Louis Armstrong And His Hot Seven represent jazz, and Blind Willie Johnson represent gospel blues. Otherwise, the music selections trend classical and worldly: Bach, Mozart, Beethoven, and Stravinsky are included; there’s an Indian raga, Azerbaijan bagpipes, a Mariachi band. (You can see a full tracklist here.)

In a new interview with the Associated Press, Ferris says that he believes what went up in the Voyager probes was “a terrific record” and that he has no “deep regrets” about what was selected. “It’s like handfuls of diamonds. If you’re concerned that you didn’t get the right handful or something, it’s probably a neurotic problem rather than anything to do with the diamonds. If I were going to start into regrets, I suppose not having Italian opera would be on that list.”

NASA estimates that the records will last 1 billion to 3 billion years or possibly more. “Voyager could be captured by an advanced civilization of beings that don’t exist yet…” Ferris said. “It’s literally imponderable what will happen to the Voyagers.”