I have been a hurdy gurdy player (google it) for 13 years now, and always wondered if one can build a polyphonic hurdy, that can play multiple different pitches at the same time. Instead of building an instrument from scratch, I decided to modify my own instrument by exchanging easily replacable parts:

I have build a second row of keys into a new lid that I could easily attach to the instrument, that operates the 2nd of the two melody strings that were there in the first place.
Additionally there is a spring-loaded mechanism that will active the 2nd string only in case I press one of those additional keys.

While I am far from done, my current instrument greatly enhances what I can play on the instrument, and I'd like to share in the talk my passion for little mechanical soundproducing boxes, the initial idea and how it evolved over time, some good Ideas (and some Ideas that turned out bad), and the message that EVERYONE should consider modifying their music instruments in the way that suits them best.