I re-read a load of the interviews on BOCpages recently and pulled out a few choice quotes. They're more or less chronological. I didn't bothered with attribution, you can search the text on the website if you like. Obviously it proves nothing, but it adds context. It's BOC/ or someone who did their homework properly.
"We were both about 10, something like that. We had started playing instruments even younger, and very soon we were playing around with recordings on cassettes and magnetic tapes, making audio collages. We began writing and playing music in a more serious way at some point around 1987”
“(Michael) When i was around ten years old, i got an old mono cassette recorder and started recording piano pieces with it. I started borrowing instruments from my friends afterwards, things like electric organs. The first time that I played a synthesiser was around 1983, when my music teacher bought a Juno 60. I got addicted to that thing. When he heard some of my home recordings he arranged a way for me to play for a studio. I created a few tracks, this is in 1983, when I was 12 years old, and from there I started forming many bands, all of them different from each other, but always with some electronic instruments"
“We started in the late 80s playing together in a guitar band but using a technological environment like samplers or synths, in the same way as Killing Joke, Nitzer Ebb or My Bloody Valentine”
"We sounded a lot more Gothic, much closer to experimental rock”
“We've been making music since school in the 1980s and no one will ever listen to it. Our friends and families are the only ones who hear everything we write and that's what we really matters”
“We've always been quite prolific and back then all that mattered to us was to give all our friends copies of our music, so we started making up tapes and packaging them, and circulating them. It was just for the love of it so we never asked anyone to pay for them.
“We've got all these tapes and discs going back 15 years or so”
“Every so often we rummage through old tapes and if we discover a melody that makes us feel something, that makes us nostalgic, we rework it”
"We might use a video we taped ten years ago, that we listen to like that, and we take one word from it. We let ourselves rediscover things by chance.
“Two weeks ago we got back to work on a song that we had not touched for two years. For us, music is never finished”
“We even sometimes recover a melody from some of our older music and go look for the rhythm on another”
“Sometimes we dig out an older melody which we wrote maybe ten years ago, and we re-work it, such as 'Turquoise Hexagon Sun' on this album. Usually we let the rhythms fall into place on the melodies”
“I guess one year we might hunt through it all and release some of it”
“Mike: We still play live instruments all the time… We record music like this a lot, though we just haven't released any of it on the scale that we are releasing the Boards of Canada tracks. But one day we will”
Eoin: We both play piano as our first instrument, and we both play guitar. Mike's a good drummer, and you can hear bits of that in there, too. We record a lot of stuff that doesn't make it onto BoC records because, stylistically, it doesn't fit. Maybe one day, we'll put that stuff out somehow.
"A couple of years ago we decided to start collating and cataloging all our early recordings, just for ourselves really, to know that we could tidy it all up and hand it on to our kids someday, but there are literally thousands of tracks going way back into the ’80s. It’s a huge task, and this just seemed to eat up time. We’ve been working on new music all the time throughout this, so we have a lot of material to wade through."
"We kept surprising ourselves, finding old things we’d completely forgotten about. We have cases full of tapes. The thing I notice about the really early stuff is how empty and abstract a lot of it is, so that reminded me of my love for a kind of “distance” in the music.”