Basics
Reading chord symbols
Decoding the chart — Δ, m, °, ø, 7, 6 and the manouche shorthand you meet on every grille.
The grille uses a compact shorthand. The basics: a plain letter is major (A). An 'm' means minor (Am). A number is an added note — 6, 7 or 9.
Δ (a triangle) means major 7: AΔ = Amaj7. mΔ (or m7M) is a minor-major 7. Don't confuse Δ (major 7) with a plain 7, which always means a dominant seventh.
° means diminished 7 (A°). ø means half-diminished, i.e. m7♭5 (Aø). 7+ or +7 means an augmented 7 (aug7).
A slash like Am/C means an Am chord with C in the bass. A % sign means 'repeat the previous bar's chord'.
In manouche you'll constantly choose between Am, Am6 and Am7 by taste. The chart writes what the composer meant; the extra colour is your call — that's a voicing choice, not a change to the tune.