The Key of G — Fiddle
The tonic, subdominant and dominant chords, and what this chair plays across them.
G major harmonises to G – Am – Bm – C – D – Em – F#°; G minor to Gm – A° – A# – Cm – Dm – D# – F. Most of the country repertoire in this key lives on three of those chords — the tonic, the subdominant and the dominant — plus the relative minor when a song wants one darker turn.
The fiddle chair carries pads under the verse and the turnaround answer between vocal lines. A chord on a bowed instrument is really a choice of double stops — two strings at a time, drawn from these tones — plus the arpeggio the bow can walk through the rest of them.
Learn the tonic-subdominant-dominant grammar in G until your hand goes there without asking, then add the relative minor, and most of the repertoire in this key is already playable.