From What I have learned, there are many types of Synesthesia. Mine in particular can only be equated to ripples in/on the water, but in a 360 degree dispersion. No colors, but it is as if I can see the physical properties of sound propagate thru open space. The "ripples" are in tune with the frequency, - low Frequencies have bigger ripples, and higher tones are tight ripples almost like vibrations in the air.
I just wrote a thread asking for people's information on the matter, but it hasn't been posted for discussion yet. I can tell you that many people that have Synesthesia are musicians. But like I said.....It depends on the type of Synesthesia he or she has.
And even though I don't condone the use of some drugs......
I've seen it happen, and seems to work with Peyote the best. This however is NOT how I experience the effects of Synesthesia.
As far as a soothing effect - it can be incredible. I find myself dozing of in my sound room playing intense rock music, at 120 db plus. Strange? Sure. Do I give a F***? NO!
I hope I shed some light on the subject and look out for future in depth discussion on this topic.
Andrew
Synesthesia Studios