D as a Nashville Chart Sees It

Count off in D and the seven numbers name D, E, F#, G, A, B, C# — in that order, every time, on a page that never mentions D anywhere.

Three of those need a mark and four do not. A bare number is a MAJOR chord, so 2-, 3-, 6-, 7- are what a chart writes when it wants the chord the key would have supplied anyway; a bare 2 means the writer wanted something else and meant it.

A bass player reads a root per number, and the slash marks that override it — the only player on the floor for whom a 1/3 is an instruction rather than a colour. Most of what is written above the number never reaches down here; what does reach is the root, and whatever a slash mark says to put underneath it instead.