"But there are other reasons I avoid copyrights. I respect people's work and just don't use it if I can"

I find this statement puzzling. The best way to respect people's work is to perform it, and that may include recording it. Copyright does not exist to prevent music from being performed, it is there to protect creator's rights and ensure they are rewarded for their work. Copyright arises automatically, but many creators choose not to exercise it, either expressly through creative commons or implicitly by not joining a rights organisation to collect royalties on their behalf.

You have already shown respect for these rights by trying to track down the rights holder. If, as Anglo says, it was written as a wedding present for Gordon Bok and his wife that might suggest that this gift included the rights to the work. In your place I would contact Gordon. If he did not feel able to give permission then I would record it with a clear conscience, knowing I had done what I could to seek permission.

It goes without saying that it should be properly attributed, and should the actual rights-holder make themselves known at a later date then you should offer to pay the appropriate royalties, if they want payment. I think it is very doubtful that even in a society as litigious as the USA a rights-holder would bother to sue over only a few dollars which you would be willing to pay anyway. Certainly I would be willing to take that risk.