There's more to Kass's song than meets the ear.
The Legend of Zelda: Breath of the Wild, an iconic game that has already saturated the internet with content. From hidden secrets to placement on the multi-pronged official Legend of Zelda timeline, just about everything has been covered.
Except for the objective date of the game according to real world standards.
I can hear you typing the angry comments already: Oh my goodness, Colin, what a pathet-
Jk Jk, I'm not nearly relevant enough to get those kinds of comments.
So how exactly do I plan on objectively dating a video game taking place in a fictional universe containing both futuristic and archaic elements in tandem?
By picking what I want to look at and ignoring the rest.
Specifically, I will be looking at the instrument that Kass plays and using it to argue a date of at the very least, post 1925.
What the hell does Kass even play?
That's a very good question and starting off point. Let's listen to Kass's theme.
The common answer is accordion. It's the instrument listed on Kass's page on Gamepedia's Zelda Wiki and on Zeldapedia.
This answer isn't wrong per se... But it's kind of wrong.
What's correct is that the sound is definitely a free-reed instrument, but that includes everything from the accordion to the harmonica, and I think we can all agree that Kass is definitely not playing the harmonica. Or the melodica. (can someone tell the Melodica Men to redo their Zelda medley, but wearing feathers plz?)
Quickly looking at Kass's instrument and a traditional accordion is proof enough to throw doubt that what Kass is playing is an accordion. I mean, just look at the two.
They share the accordion bellows, but aside from that, the size, shape, and manner of playing is completely different.
I'm not the first one to pick up on this either. A quick google search for 'what instrument does Kass play in BOTW' will return this reddit page alleging that Kass plays a concertina, more specifically one of the giant square concertinas often dubbed a 'bandoneon' (think argentinian tango).
I agree with most of this post except for the last statement about the button layout of accordions. Yes, the piano accordion has two visually different button layouts (a piano side and a bass note side), but I think the OP is forgetting about the prominence of the chromatic button accordion, an instrument that does away with the non-ergonomic piano structure and replaces it with even more buttons.
Though admittedly the buttons do look slightly different.
What gets me on the difference here is the placement of the buttons. On an accordion, you'll notice that the buttons face outward, like in the above picture. Same with Kass's instrument.
On the concertina, the buttons face to the sides, in part because both hands are being used to open and close the bellows, and having the buttons position like that make it easier for your hands.
I play the concertina so I can say these things.
The last instrument I want to posit is the 'melodeon' which often dubbed a 'diatonic button accordion'.
This one has outward facing buttons, a lot fewer buttons than a traditional accordion (though traditional accordions don't really have standard button number), and it's small enough where you could move both sides open and closed like a concertina, but from the videos I've found, it looks like you still just move one side.
With all that said, I'm gonna say that Kass's instrument, due to it's size, shape, and style of playing, is a bandoneon with melodeon-inspired buttons.
Okay but then my problem with the bandoneon being bisonoric.
Do you have a harmonica near you? Do you have a memory of playing a harmonic in your memory? Well play it or revisit that. Note how when you breathe out and breathe in, the notes change.
This is what we call a bi-sonoric set up. Bi = 2, sonor = sound.
A traditional accordion is unisonoric, having the same sound on both push and pull.
Unless you have like 500 keys on your instrument, a bisonoric key layout means that you have a limited set of notes you can play on the pull and a limited set of notes you can play on the push.
We see here that Kass has seven buttons per side of his bandoneon (top button hidden by his feather). So there is definitely a limitation to the notes he can play. Which brings me to my final point.
There is no way in hell that Kass could play Kass's Theme on a bisonoric bandoneon, and therefore he must be playing a unisonoric bandoneon, which didn't come out until 1925.
That's about it.
If you watch the idle animation of Kass while he plays his theme (not during a cut scene, just when he's chillin') there is no method to the opening and closing of the bellows. If you watch long enough, you'll see Kass play the same measures of song with both push and pull.
As we've established, that'd be impossible with the limitations of a bisonoric bandoneon.
So! The answer must be that he's holding a unisonoric baneoneon, and that only came out...
Now my non-existent haters may be saying: But Colin, what about all that Sheikah nonsense. That's super high tech. What about the Guardians?
Be quiet. Hush.
The best defense I have of that is that the Guardians and the Sheikah nonsense reflect fiction and fantasy, more than an instrument that is very clearly ripped directly from the real world.
Plus, if you were to look at real world robotics, not only would it be more of a stretch, but it would also still date the game post-1925, so like, who's thesis remains? Bam.
Go forth and listen to good folk music.