I hope that all of us on this list who work with the hearing impaired and fit hearing aids are quite aware of the fact that we must indeed fit to both the ability of the "system" and the "desire" of the individual listener. And, yes, Barbara you are quite right in the fact that one fits Alzheimer's patient quite differently from the professional musician. You are not alone in this assumption and there are many of us here who are extremely successful in our fittings as well. Your references, tho a bit overkill, are greatly appreciated. And Tom, too is correct in his statement that we have an auditory system that is not working correctly and doesn't want to respond to the desire so we have certain "prescriptions" to follow. I belong to an association of both professional and amateur musicians with hearing loss and their concerns are evidence of that fact...that as strong as the desire is, when you have a cochlea with dead or physiologically- challenged regions, you can have all the neurotransmitters and synapses and psychological desire as possible, but that person is just not going to get the same "timbre" and effect that s/he desires, but only a gross approximation, because of both the limitations of the pathological ear and the hearing device.
We are limited in achieving our perceptual desires by two very important facts: a nonfunctioning entry point of sound (the cochlea) and the "tool" we use to correct this (the hearing aid). I won't even address here the issues of auditory dys-synchrony or central disorders...that truly would be opening another can or worms.
The truly successful fit is one that manages to blend both the physical system and the psychological desire to optimize both given the very obvious limitation.
And we will always have ITD hearing aids no matter how well we fit them.
Harriet Jacobster, Au.D., CCC-A, FAAA
Board Certified in Audiology