Here's the secret that makes everything portable — Nashville studio players invented it so a song could change key mid-session without rewriting a note. That G–D–Em–C song? In numbers it's 1–5–6m–4. Move to the key of C and it becomes C–G–Am–F — the same numbers, new letters. The numbers are the song; the letters are just today's key. Reading the numbers is three rules: a plain number is a major chord (1, 4, 5) · a dash or small m is minor (6- and 6m both mean the sad cousin) · a little ⁷ means add the seventh (5⁷ — the Question with its pull sharpened). That's every symbol Beginner Mode uses, and every chip on this site shows both the number and today's letter, so you learn the map instead of one town.