This isn't a trademark question, it's a copyright, contract, and estate question.
Your query states that the publishing company owned the tapes as of 1975. It dosn't matter that the company owner died since the IP would have been owned by the company.
Your query also states that the pubishing company sold the tapes to a buyer in 1979. But the publishing company kept selling the tapes, so did the publishing company retain the copyright and the right to reproduce and sell the tapes, and just sell 1 copy to the 1979 buyer, or did they retain a license to do so from the 1979 buyer?
It doesn't matter that the 1979 buyer died, except that it's his heirs who get whatever interest he owned in the tapes and their copyright. And I'm not sure the secretary had the right to create the derivative transcription of the tapes, since it's unclear what rights the 1979 buyer had.
But is clear is that if you're not an heir or lawful buyer of the transcripts, you can't rightfully possess or sell them.
See your own IP lawyer to fully disclose and investigate all the facts.
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Unless there are unusual facts, the publishing company owns (or at least has a license for) the copyrights in the material that appears on the tapes and cds. The transcriptions made by the secretary constitute derivative works and in all likelihood cannot be sold or published without violating copyrights owned by the publisher. The fact that the owner of the publishing company died, or the man who purchased the tapes died is irrelevant. Copyright protection generally runs for the life of the original author (in this case the hypnotist) plus either 70 or 95 years depending on various technical circumstances. It is highly unlikely that the copyrights have lapsed. Thus, in all likelihood, you could not publish or distribute these transcripts without violating copyrights owned by the publisher.
Your best course of action for offering these would be to come to an agreement with the publishing company. It appears that they would have the right to prevent you from selling or publishing these on your own, but might have an interest in making a deal with you as they are in your possession.