I'm a sucker for any tools that help a musician work in uncommon scale's. Sean Luciw has released a free Vst plugin that specializes in the ancient solfeggio frequencies. He has also written a book that looks to a fun read called "Chaos in Boxes” ...“Chaos in Boxes” is a collection of experiments, theories and observations regarding music theory-based ideas and their connections to other parts of the world. Astronomy, astrology, geometry, arithmetic, science, art and poetry mix with scales, modes, chords, fretboard diagrams and more, in a down-to-earth, fun style. Check out his entertaining and informative blog here.
Sean has created a VSTi synthesizer which specializes in producing the Ancient Solfeggio frequencies. It's available for download here: Ancient Solfeggio Synth VSTi
The synth is FREEWARE, but if you feel inspired
to do so, you could click the Donation button to support Sean.