"...as my hearing aid loss is only slight (I believe it is sloping down to 20 db down at 10,000 hertz). "
I am an audiologist by profession and a stereo nut by fate for decades now; and what you describe is in fact, normal hearing as the range of normal, for an adult is considered down to 25 dB HL (a scale based upon "average" normal hearing). Most commercial audiometers do not measure beyond 8 KHz as well, as the primary concern is for speech understanding, not music. Another point to consider, is that only relatively newer hearing aids are even designed to amplify beyond 5-6 KHz, and they have extremely weak outputs by the time you approach 8-10 KHz (approx 60 dB spl which is likely not audible for anyone with even moderate hearing loss in that region, let alone conveying any dynamic range at all). Yet another fallacy is that an online app can measure hearing sensitivity at 13 KHz with anything resembling accuracy.
Basically, if it sounds better to you, then great... enjoy the music. Music programs in hearing aids generally disable the extra signal processing used to attempt to enhance speech, as well as noise-reduction. There are many things going on in modern hearing aid circuits, and the algorithms may enforce very different levels of compression depending on the frequency of the sound. Sometimes, the patient knows best. There is one manufacturer, who has a interactive programming app that allows the patient to modify many of the fitting parameters by moving the mousing cursor around the computer monitor (while listening to music through the hearing aids if desired). I find that this is extremely beneficial when my patients need to "fine-tune" their settings beyond my best attempts.
Sorry for the long response, but I could probably go for hours on this.
