This thing about British reed styles is quite interesting, because the original question was about the use of "French" and "Close toned" reeds on the same instrument.
Well, maybe the answer is most obviously to be found on the organs of Arthur Harrison, where the flambouyant Swell reeds have real devil and splash, not far removed from French reeds or those of Fr.Willis, and yet, on the same instrument, those fairly close-toned Trombas, over-powerful Tubas and Pedal Ophicleides.
The point about the Harmonics resgister (a type of Cornet with an added Septieme at 1.1/7th pitch....17.19.21.22) is interesting, for it did limit the brightness of the Great choruses; reducing the effect of the higher pitches to almost a gentle tinkle, and in no way offending the blend of the Trombas.
Arthur Harrison got away with this simply because he regulated his pipework to the n-th degree, and thus avoided a clash of tonal personalities....but was it ever ideal?
I know that great discussions and experiments took place at the Norman & Beard works when close-toned reeds first became fashionable. The voicers were very aware of the problem of blend bwteeen them and the flue registers.
All's well that ends well........we got cinema organs and endless hours of fun! (Marcel Dupre played one in Paris for a little while!)
Who else could blend keen strings, mild Diapasons, heavy Tibias, thin Vox Humana sounds, spikey sounding Kinuras, Oboes, Clarinets,gentle Flutes, Dulcianas, Celestes, cloying Tubas and brash, flared Post Horns?
It just had to be Hope-Jones and Wurlitzer!
And who took over the Hope-Jones interests?
Norman & Beard of course, who went on to make "Christie" theatre-organs when the company became Hill, Norman & Beard.
MM