It turns out there is an easier and more straightforward way of tweaking the music program using the Headphone + Hearing Test of Peace (Equalizer APO). Here is a link that describes how to do it.
I used that tool to fine-tune my music programs (guitar and headphones/music). I mirrored the frequency response of my DT 770 Pro (from RTINGS) and tweaked my guitar program using the 80 phons curve, and my headphone/music program with the 60 phons curve. Whenever needed, the target gain in my hearing aids was increased or decreased to achieve the flat response shown in the screenshot below.
Here is a comparison of the music program I crafted (solid lines) versus Oticon’s MyMusic program (prescribed targets - dotted lines).
