Here's my Lego Ukulele. It's not the first one ever, I have seen others on the internet. Still, I'm quite proud of it. There's no glue involved, and the only thing that isn't a Lego is the strings.
It ain't the prettiest, being made from a random pile of old Legos, but it is functional.
I had to find some special Technic gearbox pieces online to make the tuners.
There's no frets and it tends to get out of tune easily due to the loosening of the blocks so it is difficult to play, but it sure is fun to be able to make music with some plastic blocks and nylon string.