Someone asked me about reverse engineering ice cream truck music boxes so I did a search for one on ebay and, well... here it is.
I'm halfway between "so cute!" and "I don't know what I expected".

apparently this is the Omni 2 from Nichols Electronics, and the Omni 2 was designed when the original music chip for the Omni was discontinued.
Which says a lot about how these work...

I figured modern ones would be mp3s but older ones would just be some FM synth chips and a ROM chip of songs, but apparently they were using some all-in-one chip that had 32 songs programmed into ROM

I can see why people would want me to tear these down. That sounds weird and fun.

So there's an article about the company here:
https://blog.thecurrent.org/2016/07/the-leading-manufacturer-of-ice-cream-truck-music-boxes-calls-minnesota-home/

The company is (or was, in 2016) run by Mark & Beth Nichols. Mark's father started the company in the 50s.

and they've got this picture of one of the older machines:

And a view into the open top.
It's a music box! That's a metal record of little holes that trigger notes to be played.

And the article mentions that he's working to digitize these older songs.
I think that's exactly what's happening here:
He's got some power hooked up to run the motor, then he's going through that stack of "records" on the left to capture off the audio.

They're still around and you can still buy brand new boxes here:
http://nicholselectronicsco.com/ 

they seem to be the main maker of ice cream truck music systems.
Although there's another company's device for sale on ebay which has a selection of animals.

there aren't many for sale on ebay and they're selling at the same kind of prices as the new ones.
(and from users like icecreamman4life)
so apparently these are still valuable used and/or they're rare and collectable

I kinda suspect it's the latter? and there's a simple reason why, and it's already been mentioned on one of the webpages linked in this thread:
Turkey in the Straw.

So one of the traditional ice cream truck songs is called Turkey in the Straw, and it's a very old tune, dating back to the 1820s. It got associated with minstrel shows (done in blackface) in the 1870s and rewritten into a couple differently-named racist songs with the same tune

so the only difference is the lyrics... and ice cream trucks have been playing this song for a long time because it's in the public domain, but they play just the melody.

so back in June, Good Humor (who make lots of ice cream and other frozen treats) write about how the melody is associated with racist songs, and they later posted that they were working with RZA (of the Wu-Tang Clan) to make a new ice cream truck tune.

So naturally this isn't just as simple as "oh, it turns out that's racist? let's drop it" because it's not just "a racist song", exactly. The tune predates the couple of racist versions by a good 40+ years.

but at the same time, it definitely is the same melody and it's been affiliated with racist shit for, what, 150 years at this point?

so it's that perfect storm sort of situation where anyone wanting to replace the song is going to get opposed by people who nitpick that the tune isn't racist itself, per se, plus people who have lots of positive nostalgia for the tune and only know it from ice cream trucks...

as well as actual racists, of course.

so yeah. I wouldn't be surprised if the controversy around if the tune to Turkey in the Straw is racist has caused a run on old ice cream music boxes on ebay.

both from people who want to document the song and its use in music boxes, and from anyone opposed to it being phased out (whether they're racist or not)

But there've been articles written by multiple publications arguing "The ice cream truck jingle has racist connotations!" and "the ice cream truck song isn't racist", both of which are true to some degree because they're arguing slightly different things past each other

the ice cream truck jingle started as a 1830s song which wasn't racist: so yes, you can argue the song isn't racist, and have evidence to back it up.

but at the same time, the melody got used for a couple racist songs, and even the non-racist original song was a staple of racist minstrel shows, and the version used by ice cream trucks has no lyrics to disambiguate which version it "means" (and to some degree, does it matter?)

so saying that it's got racist connotations is also true to some degree, and there's evidence for that too.

Tie that in with everyone who doesn't care it's racist, but are just against people "banning" it? this is not an argument that'll end anytime soon.

I don't think anyone has actually suggested banning it, for the record. Good Humor basically just went "Hey, you know that ice cream truck song? Fun historical fact: it's got racist connections! maybe we should use different songs!"

there's not any laws about what ice cream truck songs you can play and no one is gonna confiscate your ice cream music.
Good Humor didn't even say "we won't sell our products to anyone who uses that racist song", which they certainly could have.

Anyway, all the attention paid to ice cream music boxes means that:
1. I can't get one for cheap enough to tear it down
2. I don't think I'd want to even if I did