I was finishing off my weekend listening to Ton Koopman playing a couple of the old organs of Groinigan and Amsterdam and I remembered the strange sound of the organ in Embrun, which I heard last month.
Here's the Wikipedia article on the cathedral
http://fr.wikipedia.org/wiki/Cath%C3%A9drale_Notre-Dame_d'Embrun
And an article on the organ, which dates from maybe 1464 and still has mechanical action
http://www.atelier-quoirin.com/Embrun_etude.php
(there is an option for English).
But the only recordings I can find, are here
http://www.youtube.com/watch?v=juDlKIDTsac
and a CD (seems to be only available as a download)
Michel Corrette played by Jan Van Mol
http://www.qobuz.com/fr-fr/album/corrette-pieces-dorgue-jan-van-mol/5425016540848
I suggest listening to track 9 onwards for the rich but unfamiliar sounds and colours of this instrument. And strange pitching.
Another online version (which is more complete but not the whole disk). The first track after the introduction isn't that strange but the following tracks are using stops which sound quite unfamiliar
http://radio.omroep.nl/f/87010/
Interesting that it's a Dutch organist rather than a French one who is motivated enough to get a CD published.