One thing one could try that, though is not directly Synesthesia, might feel somewhat like what it's like for a multi-synesthete as I am. Yet, I am also looking at something else. A way of both reviving memories and possibly of seeing if one can spark energies, even memories in others.
The first thing would be to pick a place that one could go to every day. Whether inside or out. Somewhere that is pleasant and memorable to oneself. I would recommend that there be scents and sounds, whether natural or provided. A babbling brook, music, smells of grasses or incense. Very definite sensory cues for as many senses as possible. To eat lunch there every day, even.
When this has been determined, then decide on a simple object. A stone is good. A crystal is fine, a piece of wood. But, something simple and something you can grasp firmly. You will want to keep this object with you as much as possible. Once you are finished being in the area for the day, wrap this object up in some sort of piece of cloth. Keep it in your pocket if you wish. Sleep with it under your pillow.
When you are in this place that you had settled on, try to be there every day at the same time as much as possible. Try to be there for about the same length of time. Take out your object from the cloth and set it near you. Take a certain amount of your time to observe everything around you. Smell the airs, listen to the sounds, eat your lunch or snack, feel the arms of the chair or run your hands in the grass, look up into the trees or around the room. Focus on it all as much as you can.
Then for a certain amount of time take your object into your hands and close your eyes. Think about the place you are in. Envision the area, listen to the sounds, breath in the airs, remember what you have eaten and try to taste it again in your mouth. Try to see what you can of the space you are sitting in.
As you do this, feel the energy in your hands infusing your object with what you are experiencing in your mind. After a few moments, envision the object soaking in the energies of what you are feeling and thinking. Just feel the energies passing from your hands into the object.
Before you open your eyes again, take the cloth and wrap your object back up. Open your eyes when you are ready and put your object away where-ever you keep it.
When you have done this several times, you will want to try being in another place by yourself and trying to take the object out to quietly hold in your hands. Close your eyes, sit and see what comes to you.
The idea of it being somewhat like how it is for a multi-synesthete is the possibility of the object releasing the memories 'all-at-once'. The sights, sounds, smells, taste, touch. When I sit beneath my trees at home, all my senses are melding at once. I feel the trees, see the breeze, smell sounds of the birds as well as hear them. The glittering tinkle of golden light that filters through the leaves. It's all very subtle, but all very real.
What I am presenting is not the same, no … but a rush of memories, or flood, might just push things a bit. Of course, I'm also looking for imprinting. Imprinting objects. It's an area I've worked with before and think it would be interesting to try again. I feel energy very strongly and see it to some degree. Can we reach out, can we change the way we communicate if we can really start understanding how energy works in ourselves and others?