Oooh, more specific detail by Eric Stewart (of 10cc) himself. I love wild recording stories like this.
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"It worked, but the loop itself — and this is where it gets interesting — had to be made up from multiple voices we'd done on the 16-track machine. Each note of a chromatic scale was sung 16 times, so we got 16 tracks of three people singing for each note. That was Kevin, Lol and GiGi standing around a valve Neumann U67 in the studio, singing 'Aahhh' for around three weeks. I'm telling you; three bloody weeks. We eventually had 48 voices for each note of the chromatic scale, and since there are 13 notes in the chromatic scale, this made a total of 624 voices. My next problem was how to get all that into the track.
"I mixed down 48 voices of each note of the chromatic scale from the 16-track to the Studer stereo machine to make a loop of each separate note, and then I bounced back these loops one at a time to a new piece of 16-track tape, and just kept them running for about seven minutes. Because we had people singing 'Aahhh' for a long time, there were slight tuning discrepancies that added a lovely flavour, like you get with a whole string section, with a lot of people playing. Some are not quite in time, some have slightly different tuning, but musically a lovely thing happens to that. It's a gorgeous sound. A very human sound, very warm and moving all the time. Anyway, after putting the 13 chromatic scale notes back onto the 16-track, it meant there were only three open tracks left!
For the a cappella backing of 'I'm Not In Love', the group multitracked themselves singing each note of the chromatic scale to a 12-foot tape loop. These were then recorded onto 13 tracks of a 16-track reel, and the band then pushed faders to 'play' chords. "On one mono track we put a bass drum and me playing the Fender Rhodes piano as well as bumbling a guide vocal very, very crudely, just to keep the song's timing. Kevin actually did the bass drum using a Moog bass note; a funky sound with a little edge on it, a little click almost. The timing had to be perfect, with no metronome! Then, all four of us manned the control desk, and each of us had three or four faders to work with. We moved the faders up and down and changed the chords of the 13 chromatic scale notes as the chords of the song changed — 13 tracks on a 16-track tape, fed through the control desk faders, back out of the master fader and onto that stereo pair of open tracks that was left free on the 16-track machine. It took a long time before we thought we'd got something really interesting, but blow me down, if we hadn't got it right we would have been buggered, because at the point in time when we had that stereo pair of the whole backing track mixed down, I would have to erase those 13 continuous voice notes in order to give me 'clean' tracks to start doing the real vocal, the answer backing vocals, the bass solo, the grand piano solo and the rhythm guitar, which was just a DI'd Gibson 335.
"Luckily we got it. We got it just right. We very, very quickly got the lead vocal down and then we sat there, I tell you seriously, for about three days, just listening to this thing. I was looking at Kevin and the other two guys saying 'What the fuck have we created? This is brilliant.' We knew we had something very, very special, very different. I'd never heard anything like it in my life.
Well, when we listened to 'I'm Not In Love', he kept saying 'It's not finished, it's not finished,' and I remember saying 'What do you want to try next? A fucking tambourine solo in the middle of it? What do you want?' We kept thinking and kept thinking, and Lol remembered he had said something into the grand piano mics when he was laying down the solos. He'd said 'Be quiet, big boys don't cry' — heaven knows why, but I soloed it and we all agreed that the idea sounded very interesting if we could just find the right voice to speak the words. Just at that point the door to the control room opened and our secretary Kathy looked in and whispered 'Eric, sorry to bother you. There's a telephone call for you.' Lol jumped up and said 'That's the voice, her voice is perfect!'
"We got Kathy in the studio just to whisper those words, and there it was, slotted in just before that bass guitar solo. And it fitted beautifully. Again, another little twist of fate, an accident that wasn't on anybody else's songs. We'd never heard that before. It just clinched it and made the song even more original. Poor Kathy was bemused. She didn't want to go in the studio, we had to drag her in, but she was very, very sweet and we eventually persuaded her: 'You've just got to whisper. Just whisper, don't worry. You're not singing, just talking. Use your best telephone voice.' She had a gorgeous voice, and there it is; it's on the record... and she got a gold record for it, too."