I understand what you're getting at, and I can appreciate it, but it's also kind of bullshit. You say "instruments have a sort of soul and that can inspire musicians which leads to better sound" - well, if that's the case, then people should be able to hear the difference in that sound in blind tests, which so far they basically haven't.
Are the studies blind or double blind? If the musicians do not know what they are playing, they will not be able to “respond” to it.