Yep - your memory is worse than you fear. The organ accompaniment was composed by their keyboard player - hence the case. The Bach connection is because in the bass line it bears a passing resemblance to the first 3 very well known bars of "Air on the G string", a fairly common descending bass pattern, and the harmonic structure is also very Bach-like. You could almost say "in the style of", and any keyboard player who had lessons beyond about grade 4 would recognise the general style and be able to imitate it. But Bach it aint.