Sedi wrote:
I wouldn't be sure how to separate "breathiness" from complexity...
For me they're completely separate qualities.
Being a longtime fluteplayer I've experienced firsthand the thing that happens when your embouchure develops and you acquire a more focused airstream: the breathiness/noise/dirt decreases while the richness/complexity of tone increases.
In other words far from being hand-in-glove these two aspects of tone are diametric opposites, on the flute.
On the flute everything comes from focus. The power of the low notes and the sweetness of the high notes both become greater, the tone becomes richer, flexibility increases, efficiency increases, noise decreases.
When I had to stop playing flute and turned to the Low Whistle as the closest available comp my feelings about whistle tone were influenced by my flute background. I immediately rejected Low Whistles that play like a beginner fluteplayer plays, with escaping wasted air creating noise, poor efficiency, recalcitrant voicing, etc.
When I picked up an MK I thought "Finally a Low Whistle that plays like a good fluteplayer plays!" with all the wonderful things that come from a highly focused airstream. Louder AND using less air, because more of the airstream was being used to create tone, and less of it was being wasted. Flexible willingness between the registers, no having to fight the voicing and force or coerce out the high notes. Very rich gravelly tone (not the "dirt" of wasted air but the harmonics of focused air).
It's as simple as that: poorly designed whistles play like beginner or poorly-developed fluteplayers play, and well designed whistles play like skilled fluteplayers play.