Popmuze. I am not a lawyer, and strongly advise you to consult one before you go any further. Take what follows as general suggestions only, and not as legal advice, because it seems to me you’re hell-bent on not doing this the way you’re required to by law and I want no part in it.
Regarding the interviews which have appeared in the now-defunct magazine: you conducted and wrote these interviews on company time, therefore copyright in them almost certainly belongs to the company. You have to check your employment contract from that time to find this out.
The publication is now out of business but another company bought it out, so if the copyrights belonged to your employer at the time they will almost certainly have transferred to the new owner of the magazine.
You have already published twenty of these interviews in a different book, for which the new owner of the now-defunct magazine gave you permission. If the original publishers of that book want to reprint that same edition of the same book, you don’t need further permissions; if you want to publish a new edition of the same book you might not need permissions but you must check what permissions you sought, and what you were granted. It’s possible (likely, in fact) that the permissions you were given first-time round relate only to that specific publisher, and perhaps even that specific edition. If you want to publish a new edition of that book with a new publisher (including if you want to self-publish a new edition) you’ll probably need to seek permission again; if you want to publish those same interviews in an entirely new book then you first need to get permissions from the defunct magazine’s new owners again unless the permissions you were first granted specifically include such an eventuality.
Rights in your first book might have reverted to you, but all that means is that you have the rights to offer it for sale to another publisher or self-publish it. Both these eventualities would result in new editions, for which fresh permissions from the original rights-owner—the owner of that now-defunct magazine—will first be required. If you write a new book based on those same interviews, you will also have to request permission to use them again because you are not the copyright owner; if you add more interviews to the mix, then you’ll need permissions for the whole lot. And you’ll probably need fresh releases from the interviewees, depending on what the original ones said.
To answer your question: The book that's out of print has 20 interviews, for which I had signed releases. Essentially, this is a reprint of that book, so I'd like to believe I don't need those 20 signatures again. I could be wrong.
You ARE wrong. As I’ve already said several times, unless the original publisher is managing this it’s a new edition, not a reprint, so you DO need those permissions; and you need to check the releases you have, as they might well only apply to publication in the magazine or your first book (wherever they were first published—it’s not clear from your comments here).
The new interviews would be from the magazine, and the question still is, do I need permission from the magazine, the artists, or both.
To find out if you require further permissions from the interview subjects, you will have to examine the signed releases which you are in possession of. If they specify that you have permission to publish the interview in the defunct magazine and only there, then you’ll have to seek permission from the interviewees again, this time asking their permission to use the interviews in book form. If you don’t have releases for all the interviews then it’s likely you’ll need to request permission anew from all the interviewees. It could be that the magazine in which the interviews were first published held those permissions: you’ll need to find that out, track them down, and find out what permission was granted. Do not assume that any such permission was granted unless you see it in paper in front of you, or you’ll be in legal soup.
my books are so obscure that the artists wouldn't bother coming after me, even if they were to find out about it
I know of no legal defence covered by obscurity: that is, your disclaimer above is not only not going to help you, it’s a shabby cop-out. It’s disrespectful to the people you interviewed, the company which once paid your wages, and the publisher which published your previous book.
And since it's an ebook I'm planning, I could just take them out if they complained too loudly. Whereas, if I asked for permission and was denied, or more likely, never heard back from the person, I wouldn't be able to use that interview.
So, you’d rather do the easy thing and go ahead without permission and hope you’re not found out than do what’s both legally and morally right but which takes a bit of effort, and you’re relying on no one having the money to go after you if you are found out. What utter class.
Incidentally, I recently reprinted a book which contained a dozen interviews and didn't request new permission from anyone. Then again, so far it's only sold ten copies.
It doesn’t matter how many copies a book sells: if you’re using copyrighted material without the copyright holder’s permission, you’re stealing. Is your publisher aware that you don’t hold the required permission to use this material? You realise that you’ve put their business into jeopardy by doing this? The more I read about this from you, popmuze, the more weaselly you sound.
Don't want to belabor the point, but the book I recently reissued was the exact same book as I had published in 1982 and all the interviews were done for that book.
So you’re talking about using interviews from two of your previous books now? Plus interviews from the magazine? Right. Well, again, you need specific permission for every edition and every new publication. If the original permissions you were granted included such rights then you don’t need to seek them again but if they didn’t, you do, regardless of where you’ve used them before, what they’ve allowed you to do before, or what you think you can get away with.
The second book I was thinking of reissuing would be the same case, but I might rewrite the text. The third book would have the old interviews that I did for the book, a bunch of new interviews from the magazine. That's the one that could cause trouble.
Why do you expect trouble from this third book? Might it be because you know you really should ask permission to use the interviews but you don’t intend to? If that’s the case then you deserve all the trouble you get.
Maybe I should put the new interviews in an entirely new, fourth book, and seek permissions for that. The third book could then be reissued exactly as it was in 1975, with all the interviews done specifically for that book.
Unless that third book is a reprint, published by the original publisher, or you have been given the rights to use the interviews however you like, you still need specific written permission from the copyright holder to do this.
Popmuze, It doesn’t matter how many times you ask the question, you still need specific written permission from the copyright holder to use these interviews in your books; and you need specific written releases from the interviewees too. Hoping no one will catch you and that you'll get away with this is not the way to proceed and I am, frankly, horrified that you seem to think it’s acceptable.