Summary

Use a fishing line as strings,
Play Ukulele on an iPad mini.

the code was written by Pythonista for iOS.
https://goldengrape.github.io/code/iPad-Ukulele/Ukulele.py
You should run it in Pythonista3

You also need a guitar/Ukulele tuning button.

For detail:
read my blog

https://www.youtube.com/watch?v=w-KjJy7J-Tw