I'm recording interviews and will have an interviewer and of course an interviewee. Is offering them publicity enough? Or what percentage of sales of the audio product would you offer? It might be a hassle to track sales and send them their cut, but might attract more experts and the audio book would be of better quality. What do you think?
It depends on his wishes. He is giving you his rights to his voice, so he is pretty much able to demand a part of the sales. If he doesn't do it though, you're free to just go with publicity. Many people only want free publicity. Don't offer him a percentage unless he asks you to, or he refuses to do it for free. Negotiate a little.