Carl Sagan? Lewis Thomas? Douglas Adams? Stephen Fry? Anonymous?

Question for Quote Investigator: Suppose humanity decided to deliberately send a message out into space. What should be included in that message which might someday be read by a hypothetical alien civilization?
In fact, the U.S. launched two robotic interstellar probes in 1977, Voyager 1 and Voyager 2. Mission planners decided to include a golden phonograph record containing pictures and sounds of Earth. Apparently, one person contemplating this topic said something like the following. Here are two versions:
(1) We should send recordings of Bach, but we would just be showing off.
(2) I would send the complete works of Johann Sebastian Bach, but that would be boasting.
This notion has been attributed to astronomer Carl Sagan, essayist Lewis Thomas, science fiction author Douglas Adams, and comedian Stephen Fry. Would you please help me to determine the correct phrasing and the identity of the commentator?
Reply from Quote Investigator: In 1974 physician Lewis Thomas published a collection of essays titled “The Lives of a Cell”. One piece discussed the “First International Conference on Communication with Extraterrestrial Intelligence” which had been held in 1972. Astronomers who attended considered the use of electromagnetic signals for communicating with possible civilizations throughout space. Lewis believed that other lifeforms would probably be more than a hundred light years away. Boldface added to excerpts by QI:1
Whatever information we provide must still make sense to us two centuries later, and must still seem important, or the conversation will be an embarrassment to all concerned. In two hundred years it is, as we have found, easy to lose the thread.
Perhaps the safest thing to do at the outset, if technology permits, is to send music. This language may be the best we have for explaining what we are like to others in space, with least ambiguity. I would vote for Bach, all of Bach, streamed out into space, over and over again. We would be bragging, of course, but it is surely excusable for us to put the best possible face on at the beginning of such an acquaintance. We can tell the harder truths later.
Below are additional selected citations in chronological order.
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