Take this post with a grain of salt, since I know a lot of you are skeptical, but here's a theory I've been thinking about for the last two days:
There is a great deal of similarity between the turquoise hexagon discs on the Pioneer's Plaque and the mysterious postcard: https://imgur.com/a/Rp1EQny
They could possibly be related if you take the space theme into account. What I was thinking, especially since Flylo recently released a soundtrack for Yasuke, is that BOC might have done a soundtrack for the new Starfield game. Warp does license music to video games and other media, and they even specifically have a page dedicated to that. BOC have also been shown to be avid gamers (there's been some connections to them and Fortnite, in addition to Iraq says) so I could really see them being behind a soundtrack for a video game.
Perhaps BOC are even on a soundtrack kick after writing and producing a post apocalyptic soundtrack for a hypothetical movie.
That's my two cents. I'm probably wrong, but you gotta admit, an ambient space soundtrack courtesy of BOC would be awesome!