The Key of A — Mandolin

A major harmonises to A – Bm – C#m – D – E – F#m – G#°; A minor to Am – B° – C – Dm – Em – F – G. 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 mandolin chair carries the chop on the backbeat — a closed, muted chord landing where a snare would, and a chop is a chord with the ring taken out of it — closed shapes only, damped the instant they sound, landing where a snare would.

Learn the tonic-subdominant-dominant grammar in A until your hand goes there without asking, then add the relative minor, and most of the repertoire in this key is already playable.