oh ! @Oswyn Faux is there a relation between the medullary rays and the "flambed wood" ? (f.e. at the backside of a violin)

@jcsekinger that's either quilted/tiger stripe wood, where the grain is like sand ripples on a beach, or the chaotic crotch pattern where a branch comes off the trunk. Best example of the rays is quartersawn oak, or riftsawn oak. Oak has huge rays, maple had tiny rays

Okay, what I did to replicate the nested rings effect was use a geometry node to displace the surface of a series of nested cylinders. Because they were all displaced by the same amount they were perfectly nested. Is that how you did your nested rings?

The problem might be in the change of the functionality of the nodes due the Blender update to 4.0. It makes allot of instruction videos obsolete.

Honestly if you are trying to follow this guy as first timer don't ! probably don't even bother if unless you really want make his variotion of wood. He overly complicates things and than skips required parts. Follow Ryan King Art instead, to it also takes bit of learning curve to follow his tutorials as well.

I would definitely start with a more basic material tutorial first but don't give up. I personally like this one because since it's procedural, you don't have to mess with UV maps which depending on your object can be a huge headache. And the result is very close to realistic with some tweaks to the scale. I just stopped the video a lot and slowed it down in some parts to see what he was changing. The only parts I noticed that he changed but didn't show is sometimes he changes the values a little, but he does show the whole node setup at the end if you want to check your work. And he doesn't show the keyboard shortcuts that he uses, and he uses them a lot.