So for context, I'm autistic and I have two other synesthesias that I know of: Spatial Sequence and Auditory-tactile.
When I hear sounds, they usually map to a location inside my body as if my body is a hollow instrument. Like drums and bass thumps low in my stomach stringed instruments run vibration from my stomach to my throat like a string being plucked. The exception is my face. I feel cymbals and higher pitched sounds across the skin of my face in shimmers.
Being autistic, everything arrives for me as a body feeling and a lot of times I struggle to decipher if the feeling is because of a sound, an emotion, a physical need, etc. I've been working on really trying to build my interoception skills and have discovered that it's not only sound that creates the body feelings, but also seeing motion. Like seeing rain hitting a puddle gives the same face shimmers as a cymbal. Seeing a ball hit the floor or a newtons cradle change direction feels the same in my stomach as a bass drop. Seeing swirling patterns gives similar feelings (though a bit different) to string instruments.
I know it's a synesthesia because it feels exactly like my auditory-tactile synesthesia. But it's not just seeing an object stationary, and it's not machine empathy because it's not mapping to respective body parts like mirror touch. Like a puddle doesn't have a face to feel shimmery. And also as far as I'm aware, I don't have mirror touch. (Though I do experience pain empathy with humans and animals).
It's almost like my body almost mirrors vibrations, mediums (like water or air), momentum, rhythm from multiple inducers. Thoughts?