I have a project that is best as an audio tape. What agent would handle that?
Generally audio sales are handled as a subsidiary right. They are sold after the book is sold, and often after the reviews are in and the sales figures are in if it's an unknown.
I know of ONE guy who did an audio first, Ron McClarty, and he is a professional actor who did his own and it got noticed by Stephen King.
Gerard Jones did his own audio and if memory serves, the Great Publishing Pest (whom I just adore actually), is giving it away.
If you intend to do this solely as an audio tape you'd do well to talk to the folks who do music and spoken work productions. They know about this stuff. I have no idea how to find them but I'm guessing a quick turn down Google Lane will provide an address or two.