Just a light-hearted listening test

[Soubasse]

Don't know if you've done these before Ladies and Gentlemen, but a couple of other forums I'm on do this from time to time as a little brain-teaser for those who like to use various powers of aural deduction. I'll keep it devoid of extraneous information for the moment.

Have a listen to the attached file and let's know what you think - not of the the piece so much, but of the organ. I'd be interested in your thoughts, hypothesis, general comments.

(I will confess that I was a just a wee bit surprised, particularly given some mitigating factors known to me - and there's likely to be something in this clip that's a giveaway).