concept
A
Pitch class A — a major-sixth span from C; a presence that holds its line in the twelve-note return.
A is pitch class 9 — a major sixth above C (nine semitones), a natural letter-name, often La. It is a common tuning reference pitch (A4) in practice, but here it is only a class among twelve.
On the keyboard it is the white key between G♯/A♭ and A♯/B♭. As a pitch class it holds every A across octaves to the same step of the cycle.
In major-triad grammar A is the root of A major (A–C♯–E), the major third of F major (F–A–C), and the perfect fifth of D major (D–F♯–A). Alone it stays a pitch class. A vessel offering needs three notes that form a recognized major chord.
Also known as A natural · La