Hi there, I was in a MT program for a year before I quit, but I may have some experience and advice that may help you.
What is it about a psych PhD that you want so badly? I find it's so completely different from the MT world. MT is completely clinically based, it's all practice. While you do read about research it is weighed waaay less than a psych phd. If you like the practicing notion and learning instruments, song interventions, etc. then it may be a good fit. But if you're expecting to do music related clinical research, it's less likely. They're not built for that, maybe more so in the masters (and phd level), but still the ultimate goal is for you to go out and practice your craft. Psych phd on the other hand is very research focused, and depending on what area you want to go in (clincial?) it will be different. Clinical phd (from what I know from my colleagues) will give you experience and chances to go out in the field and work with people, however, it will still be more research based. A psych phd will be less focused in music. I almost went into a cognitive program focusing on music cognition. There are a few routes you can go for researching "music" in psychology. Cognitive, neuroscience, some interdisciplinary programs do exist. It is tricky to get your foot in the door to music related research in psych because it is a smaller topic area, and you will have to be creative on how to get there. Often times there is not a research who purely does music research (that's what a musicologist does lol), so often they will have interests in audiology or some cognitive mechanism and then it relates slightly to music as well. Of course there are the few big names out there, but other then that it is a little scarce.
TLDR; you need to figure out what exactly you want to do after graduating because these degrees will give you different things. What is it about music you like? What part of it do you want to incorporate in your future job? Do you like practicing and working with people? Or are you interested in research and the mechanisms behind music, therapy, etc. There are PhDs in music therapy, which may combine a bit more of both of the elements. However, you will have to get your bachelors and masters first, and those will at first be a lot more practice-based. Personally, I realized that practice centered focus was not for me, I wanted to do research, so I went with a psych phd.