Although I'm not familiar with what solfeggio scale forks are, I do believe sound has value for therapy of many kinds. It must have to do with our spiritual vibrations - or at least that's my opinion.
I like a few audio CD's from Dr. Jeffrey Thompson - who works with sound: The Awakened Mind System, The Alpha Relaxation System, and Sleepy Ocean (never sleep without it). I really would like to know more about other sound/music that can be found to help with healing etc.
Maybe another good example would be the Singing Bowls? Some also use these to cleanse your cystals/stones, too.
This is a nice short overview of singing bowls and other instruments being used in various ways: