My best guess would be mid 80's. Certainly it was when electric keyboards/synthesizers were really popular cause it has that airy/almost organy/piano kind of feel to it. *If you don't know what i'm talking about, listen to the intro of "Living Years" by Mike & The Mechanics if you have it, the effect is similar*
I could hum a few bars, but I don't know how to post stuff to the internet.. heh
Its not that big a deal, its just mildly annoying, that's all.. sorry I couldnt be more help