[sillysaurusx]

Thanks! Interestingly, the tape for Probability seems to be narrated by someone other than Feynman.

I should probably give some evidence to back up my claim that Feynman didn’t write all of the Lectures, but alas, it’s late. I think the credits for the rest of the authors were in the preface, or at the end. I just wish they’d gotten a little more credit.

[vmilner]

That someone is Matthew Sands:

“Early on, though, a small problem surfaced. Feynman had a long-time commitment to be absent from Caltech the third week of the fall semester, and so would miss two class lectures. The problem was easily solved: I would substitute for him on those days. However, to avoid breaking the continuity of his presentation, I would give the two lectures on subsidiary topics that, although useful to the students, would not be related to his main line of development.”

https://physicstoday.scitation.org/doi/10.1063/1.1955479

Later on he writes about the published books:

“The next stumbling block was more serious: choosing a title for the book. Visiting Feynman in his office one day to discuss the subject, I proposed that we adopt a simple name like “Physics” or “Physics One” and suggested that the authors be Feynman, Leighton, and Sands. He didn’t particularly like the suggested title and had a rather violent reaction to the proposed authors: “Why should your names be there? You were only doing the work of a stenographer!” I disagreed and pointed out that, without the efforts of Leighton and me, the lectures would never have come to be a book. The disagreement was not immediately resolved. I returned to the discussion some days later and we came up with a compromise: “The Feynman Lectures on Physics by Feynman, Leighton, and Sands.”

[triknomeister]

That's horrible move from Feynman about credit.

[lupire]

It was also a "horrible" move for the two editor/publishers to claim equal author credit for Feynman's much more extensive creative effort.

In reality, a simple negotiation led to a good decision that made everyone happy.

[vmilner]

[It’s worth emphasising that Sands was hugely positive about the lectures and was great friends with Feynman.]

[stiff]

I think these people other than Feynman transcribed and edited the lectures into book form. This seems to have been the process with most (all?) books of his, "QED" and "The character of physical law" were also delivered as lectures and even "Surely You're Joking, Mr. Feynman!" was an interview originally that was later transcribed and edited.