I'm sorry I missed this post. I got a chance to play the Aulochrome and talk at length with Francois Louis recently during a clinic at the University of Miami.
Both sides of the double soprano Aulochrome play very well. More importantly, the mechanism is ingenious and brilliantly executed. It is actually possible, with practice, to play any note on either side of the instrument with the same or any different note on the other side.
Of course, this enables the player to ply two parts simultaneously. However, after talking to the inventor, I believe his primary intention was to create an instrument capable of creating sum and difference tones, meaning that the range of the instrument is theoretically increased beyond the capabilities of either side of the horn.
I tried it and I could hear the extra high and low notes created by combining the two parts of the Aulochrome. I am still trying to perfect one note at a time, though, so I will leave it to guys like Joe Lovano to create music with these new sounds.
Problem: As I understand it, there is only one copy of the original Aulochrome with the exceedingly complicated mechanism perfected by Francois Louis, and the ownership of that instrument is in dispute. Even Joe Lovano's horn is different, and if I'm wrong, I stand corrected. But it seems, if you want an Aulochrome, you won't get it.