4 Flats: A Flat Major / F Minor
Four flats is A flat major, or F minor. The flats are B flat, E flat, A flat and D flat, and the second-to-last of them — A flat — names the key.
4 flats
A♭ major / F minor
With flats, the second-to-last flat names the major key directly: the flats run B♭, E♭, A♭, D♭, so the key is A♭ major.
A♭ major scale
A♭ B♭ C D♭ E♭ F G
F minor scale (relative minor)
F G A♭ B♭ C D♭ E♭
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A♭ major scale
A♭ B♭ C D♭ E♭ F G
F minor scale
F G A♭ B♭ C D♭ E♭
Where the balance tips
A flat major is A flat, B flat, C, D flat, E flat, F, G. Four of the seven notes are lowered and three are natural, which makes this the first flat signature where the accidentals outnumber the plain notes.
For a reader that is a real threshold. Up to three flats it is workable to track which notes are flattened; from four onward it becomes easier to track the exceptions instead — in A flat major, only C, F and G are natural. Making that switch deliberately, rather than continuing to count flats, is the single most useful habit for reading in the remote flat keys.
Comfortable on a keyboard, awkward on open strings
On a piano this key sits well. Four flats means four black keys in the scale, distributed so the long fingers fall naturally on them, and A flat major is a standard part of the intermediate scale repertoire for exactly that reason.
On instruments with open strings it is a different story, and the numbers are easy to check. A guitar's open strings are E, A, D, G, B and E. Of the seven notes of A flat major, exactly one — G — appears among them. Every other open string is outside the key. A violin's open G, D, A and E fare no better: only the G belongs. So a key that a pianist finds unremarkable offers a guitarist or a violinist almost nothing to ring against, which is why it appears far less often in music written for those instruments.
F minor
The relative minor is F minor, and its raised seventh degree at cadences is E natural — another instance of an accidental cancelling one of the signature's own flats.
F minor is a key with real presence in nineteenth-century piano writing and, later, in film and orchestral scoring, but on a guitar it inherits the F chord problem from one flat: the tonic requires a first-fret barre, in a key that offers no open strings to support it. A guitarist meeting a piece in F minor will almost always capo rather than play it as written, which is not a compromise so much as the standard practice for the instrument.
What it is used for
Four flats sits at a useful point for wind ensembles. Concert A flat reads as B flat major for a B flat clarinet or trumpet — two flats, entirely comfortable — and as F major for an E flat alto saxophone, one flat. In other words, the key that starts to strain a string player's patience is still easy for the whole wind section, which is why it turns up in band writing more readily than in orchestral string writing.
It is also a common key for vocal music, for a reason that has nothing to do with notation: A flat and its neighbours sit in a comfortable range for many voices, and singers' keys are chosen by tessitura rather than by how many accidentals the pianist has to read.
The seven chords of A♭ major
Every major key produces the same pattern of chord qualities — major on the first, fourth and fifth degrees, minor on the second, third and sixth, diminished on the seventh. Only the names change.
Questions people ask about this signature
- Four flats is what key?
- A flat major, or F minor. The four flats are B flat, E flat, A flat and D flat.
- Which notes are natural in A flat major?
- Only C, F and G. From four flats onward it is faster to remember the naturals than to track the flats, because there are fewer of them.
- Why does A flat major sound thin on a guitar?
- Because only one of the six open strings — the G — belongs to the key. Nothing else can ring, so every note has to be fretted and the instrument loses the sympathetic resonance it has in E, A, D and G.