Chess and weird head injury symptoms: Synesthesia

Wikipedia gives a definition of synesthesia which js good enough to work with here, describing it as the experience of "the stimulation of one sensory or cognitive pathway [leading] to involuntary experiences in a second sensory or cognitive pathway."  The most commonly referenced form of synesthesia in the media and in English-language colloquialism is "seeing colors," often associated with drugs.

It's also a common medical symptom of a number of neurological conditions. I've experienced episodic synesthesia ever since my head injury in 2013, and yesterday I experienced it for the first time while playing chess.

My most common sensory mixing is sound and tactile, and it's not usually a pleasant experience. I do sometimes achieve a relaxing sensation from ASMR almost like standing in a gentle shower. I've experienced synesthesia from video game sound effects many times before; it's why I always turn off haptic responses on my controls. They're essentially redundant and become confusing. 

This was basically what happened when I was playing chess. I was playing a rapid game with a 15/10 time control, and as soon as I started playing my opening (London system) I could tell something was weird. I had almost a physical sense of where my pieces were and what the position of the board was. It might have helped me if it weren't distracting, and if I had any way to reproduce it. It didn't help me or hinder me as it was, but it was a really intense game - I felt like I had physically exerted myself. My heart rate and blood pressure were moderately elevated, as they often are during and after a synesthetic episode. I took steps to prevent a migraine, as they often follow such events.

It remains to be seen whether this will be a one-time event, or something that recurs.