These drafts, everything from grant proposals, correspondence, and his books and articles, were dictated to cassettes and transcribed. When working on books in the 80s and 90s he would dictate sections, which were transcribed for him.
For example, listen to some of these digitized sections of an audio cassette that contains parts of Sagan's novel he annotated and revised. He would then mark up print outs of the transcripts and edit, revise and assemble them into drafts.
For example, Carl Sagan's ongoing ideas and reflections in notebooks from his time in college, for a brief period in a notebook in the late 1960s, and on particular topics, like this notebook on Jupiter's Moon Titan.
Sagan was not generally in the habit of keeping a notebook of his running thoughts and ideas.
Carl Sagan wrote a considerable amount of shorter pieces for magazines and periodicals.
Many of those essays would later become sections in his books.
A selection from the mid-60s through the 90s has been digitized to give a sense of the diversity of his interests.
These include everything from the properties of clouds on Venus, to the potential value of an astronomical observatory on Mars, to ideas for a science fiction novel involving the CIA and the NSA investigating UFOs, and musings on the possibilities of interstellar communication as music.
I will also admit to spooking myself out on occasion when my dog has refused to stop barking at what appears to be an empty corner of the house.
But what makes us feel like we are in the presence of a supernatural spirit?