Using 70's Voice Over in New Music Track

Dear Rich: I'm in the final stages of producing a music single. In the song I've sampled the voice-over of a 1970's TV ad. The voice-over is of a familiar and famous figure from that period. Would I need to clear this and for this purpose with whom, as I assume in this case that no record company or music publisher would be involved. We're not sure which familiar and famous person's voice-over you're using but if you're creating a second single, you might want to consider a classic 70s TV ad in which a size-challenged nautical figure -- perhaps a descendant of this character -- rides around in a boat in your toilet and urges consumers to pollute the waters with blue chemicals. How '70s is that?
Right you had a question. You're correct that you wouldn't need to clear the voice-over recording with a music publisher or record company. You may not need any permission at all, as explained below, but there are three possible legal rights you need to consider:

• the copyright on the commercial. The most likely permission needed is that of the copyright holder -- that's likely to be the ad agency that created the commercial, or the company whose product is featured in the commercial. The copyright owner would own rights to the text of the commercial and to the audio. You wouldn't need permission if you claimed fair use (which can always be a bit tricky). And you probably wouldn't need to bother with permission if the company holding copyright had disappeared and you couldn't track down a successor. (And of course, you wouldn't need permission if your song had limited appeal and was unlikely to be heard by anyone connected with the copyright owner -- what we call the "tree falls in the forest" theory.)
• the use of the famous figure's voice.  If the familiar and famous person's (FFP) voice is recognizable and listeners think that it is being used for purposes of endorsement, the FFP might have a claim based on the right of publicity. We wouldn't worry about this too much because the FFP's ROP probably won't be triggered unless the song is used for a 3rd party commercial purpose -- that is, it's licensed for use with another product or service (This article provides a short ROP summary). 
• trademark rights. If the product name (the subject of the commercial) is included in your song, that might trigger claims of dilution or infringement but both of these claims are unlikely to succeed as use of trademarks is permitted for informational (or editorial) uses such as songs. One judge characterized the conflicting interests of the parties "Speech-zilla v. Trademark Kong."