It makes me wonder how much there actually is such material. It is clear that artists was not famous for works like these, and who knows how many guys experimented with sounds that were considered at the time worthless noise.
You can see plenty of old tape music and vintage electronics emerge in public durin decades. I would suppose there is shitloads of that, but there is barely ways to capitalize it unless it is someone "famous". I think even in Finland, which is quite backwards country in technological terms back in 50's, there was already some odd electronic material created. There exists book FIRST WAVE : A MICROHISTORY OF EARLY FINNISH ELECTRONIC MUSIC that deals with 50-60's material.
I'm quite sure that many experimental studios or TV/radio broadcast efx creation studios may have these rotting reel-to-reel archives where someone was trying out things, that seemed too crude to anyone actually listen to as music. I would not be surprised if there was way more of that than found from history pages. It would seem unlikely that guys who are doing soundtracks for films, special efx, etc would not "privately" work on sound pieces and experiments. Probably just not considered to be worth shit at the time. And barely even now.
I could not spend much time with Jack Ellitt pieces like "Light Rhythms", but Journey #1 is good stuff.
https://shamefilemusic.bandcamp.com/track/journey-1And that said, I'm quite sure that journey-1 would have been considered pure garbage by most, and due noisiness and crudeness, yet I would assume that from moment when tape was invented, someone ran tests what can be done with it. I doubt that it even matters whether someone is at 30's or 60's or 80's, if there is zero reference point to be influenced by something. Just access to tape player and be amazed by what it does for sound when rewinding, pausing, altering speed. There is something so timeless about it that it would make me assume that "alternative usage" of tape is exactly as old as tape format and players themselves.