That’s exactly it. It’s a nine-string custom version of the Harmonic Master by New Complexity, which usually comes in six- or twelve-string varieties. Lewis Waters is the luthier.
I believe Lewis has been continually updating the design of the Harmonic Master, but I’ll tell you about mine.
Yes, it does have a bridge behind the pickup. The set of normal pickups and the behind-the-bridge pickup have a separate output each, but if only one cable is plugged into the guitar, then both signals come through the single cable and are blended via the volume knobs. The harmonics that ring out in the behind-the-bridge portion of the string field can be tuned with sliding tuners.
I have the lower register strings (E, A, and D in standard tuning) doubled. Before buying the guitar, I was going back and forth between whether I wanted the 12-string (for lush chords) or the 6-string (for more hammer-on, pull-off stuff). Lewis thought, and I agreed, it’d be neat to find a happy middle-ground. So he built a version where those lower-register strings could be doubled, thus allowing for those lush chord voicings, while leaving the higher-register strings for noodling. He was able to space the strings just right, so if I want to make it a 6-string with standard spacing, I can.
Regarding the utility of the behind the bridge sound: It’s super useful. To my ears, it’s a much more lively sound when I employ those harmonics. Depending on the level of the behind-the-bridge output, I can get anywhere from bell-like tones to ringing, almost reverb-like shimmers. I also frequently strum or pluck the strings behind the bridge for zither-like sounds. And then, of course, there’s the whole split output, which opens up a range of interesting possibilities for effects routing.