The resonators are simple PVC piping of various diameters! Tuning those was dead simple, just cut a section out, put a cap on one end then bang it with a hammer to produce a tone, then just chop a bit off to raise the pitch,
For the keys it was a bit more complicated, I typed out a comment giving the basics and linking to the blog I used to figure it out though!
Thanks for this. I have an old busted premier marimba with fiberglass keys and a few are cracked. Maybe I’ll make a new set because the frame and resonators and still in decent shape. Although I am sure the tuning process was a nightmare!