Soul infusion is a property of tralaticon that stores the impressions of those who come into contact with it. This phemonena is not understood in the Conduit Cities or fully by the Ergon, though both make use of it.
Soul infusion does not take a human being's soul or even diminish it, rather, when there is significant physical contact over time, especially when mixed with strong emotion, the tralaticon-alloyed object begins to absorb the skills and feelings of the user. This does not convey sentience or consciousness and there is no conversation as commonly understood, but one can feel the same things previous users felt, intuit how they interacted with the object, and how they channeled its power.
Examples are uncommon, but appear in some form across the continent. The most prized imbued instruments have lineages and are passed down from master to student. Some have been stolen or destroyed, caused fueds and even small wars. Every Sweep Team in the Census Office has a Commander's Sword which is wielded by each successive commander during battle and contains, in some way, all of their accumulated wisdom. A shaman's focus is ritually prepared in the Spirit World at the end of their training when their various spirit guides impart a piece of their souls into the focus. Despite the vast potential of these items, they cannot directly convey expertise. For instance, someone who has never played a violin cannot pick up an imbued violin and play like a master, or even well. The more skill someone has with that item, the more they are able to benefit from Soul Infusion.