I went to school in Minnesota and we had to go to a certain music store and ask a specific employee for the book. I believe it was $50. It was basically required to play jazz.
I remember when my brother (a teenager at the time) bought his book he had to give his music teachers name and the employee called for a reference.
About a year ago I finally began to work on my dream of a Forth implementation by building a Forth-based flight management computer into a spaceflight simulation game that I am working on. Now, instead of writing mostly C# or GDscript code in Godot, I am trying to figure out ways to create a useful device using this awkwardly elegant language. I'm having fun with it.
One of the interesting bits is that I have been able to make the Forth code an entirely separate project on Github (https://github.com/Eccentric-Anomalies/Sky-Dart-FMS), with a permissive open-source license. If anyone actually built a real spacecraft like the one in my game, they could use the FMS code in a real computer to run it.
There is one part of the linked article that really speaks to me: "Implement a Forth to understand how it works" and "But be aware of what this will not teach you". Figuring out the implementation just from reading books was a fascinating puzzle. Once I got it running, I realized I had zero experience actually writing Forth code. I am enjoying it, but it is a lot like writing in some weird, abstract assembly language.