All of the little music nerds will be so jealous of you and your homemade MIDI
concertina. They'll be all like "oh man, look at that awesome MIDI controller that looks like a Hayden Duet Concertina, an instrument well known for its easy playability and chording. We're so jealous." And you'll be all like "yeah, I know, it's awesome. I built it based on the design by Paul Everett, and though it lacks the actual accordion type velocity control of an actual Hayden Duet Concertina, it is still quite playable and responsive." It's going to be so great.