A certain rendition of O Come O Come Emmanuel - does anyone know who performed this rendition?

It's rather old - probably the late 1980's, because I first noticed it when I was in Jr. High. It open with the singers - probably a boys choir - singing the first line with no instrumentation (A Cappela). The are not singing the words, just "ah" - ing each note. After the first line, an organ joins them, and they continue several verses, and another group of boys joins the first boys, singing at a lower pitch for harmony, also not singing the actual words. This rendition is also quite long - I'd say at least 3 minutes, maybe closer to five.