(Thanks to Christoph Schuringa for the pointer.)
UPDATE: Michael Otsuka (UCL, moving to LSE), editor of the collection of Cohen's papers linked above, writes:
Regarding the audio recording to which you’ve drawn your blog readers’ attention: I had originally proposed that this be included as a CD in Finding Oneself in the Other, to be listened to while reading the accompanying prepared text of the lecture, which has been published as Ch. 9 of that book. PUP informed me that they would need to raise the price of the book in order to cover the cost of this and proposed that the recording be posted on the book’s web page instead. I agreed, in order to keep the price of the book down. Pp. ix-x of my Editor’s Preface to this book, which is linked to the same web page, explains why, on account of its low quality, the audio recording is best listened to in conjunction with the written text.