Okay, okay... he and I were discussing a certain bass luthier who made a very big deal about the "tone blocks" at the heels of his necks back in the late '80s. He touted it as this epiphany he had that would change bass design forever, improve sustain, blah, blah, blah....
This luthier also worked in Carl Thompson's shop as an apprentice in the '70s, although he never mentions it publicly that I know of. Now neither Carl nor I have any issue with the guy's skills as a luthier; He makes really nice basses and he's also a great player but the hyperbole in his advertising was a little much.
During the discussion Carl said "Wanna see the first tone block?" What was I gonna say, no?!? He dug around under a workbench and pulled out a bass. Beat to hell, various spots where it had obviously been routed, filled and routed again, no strings, no tuners.... it was his prototype. Carl Thompson #001. It had spent years as his test bed for anything he might want to try out and then more years covered with sawdust under a workbench. And it had an ebony tone block. In 1971.
"There it is." he said, "The first tone block. Wanna know why I put it there? Because I screwed up the neck pocket and if I filled it in with the same wood it would have looked like a mistake but if I filled it in with a contrasting wood it would look deliberate, so that's what I did. He saw this bass hanging up in the shop the whole time he worked for me. Tone block?!? Goof block is more like it!"
So there you go: Carl Thompson's take on "tone blocks."