4 flats key signature: which keys use four flats?
A 4 flats key signature belongs to A flat major and its relative minor, F minor. The four flats, in order, are B flat, E flat, A flat, D flat. On a flat signature the major name is the flat before the last one, so A flat. Four perfect fifths down from C land on the same note. The pitches to recompute are 415.30 Hz for A flat and 349.23 Hz for F.
What a 4 flats key signature prints
A flat major and F minor share these four flats and stop there. The next flat in the fixed order would be G flat. That fifth flat names D flat major, on the 5 flats key signature page. Three flats stop at A flat and name E flat major, one fifth higher.
| Flat | Treble staff | Bass staff |
|---|---|---|
| B flat | third line | second line |
| E flat | fourth space | third space |
| A flat | second space | top line |
| D flat | fourth line | third line |
| A flat major | F minor |
|---|---|
| A flat, B flat, C, D flat, E flat, F, G | F, G, A flat, B flat, C, D flat, E flat |
Diatonic triads in A flat major: A flat major, B flat minor, C minor, D flat major, E flat major, F minor, G diminished. F minor starts on F minor, then G diminished, A flat major, B flat minor, C minor, D flat major, E flat major.
How four flats name A flat
On a signature of two or more flats, the major tonic is the flat second from the right. Here the rightmost flat is D flat, and the one just left of it is A flat. That is A flat major, not the relative minor.
The downward fifths tell the same story. C down one fifth is F, down a second is B flat, down a third is E flat, down a fourth is A flat. Four fifths down, four flats. One fifth higher is E flat major, written up on the 3 flats key signature page.
F minor sits a minor third under A flat: A flat down three semitones is F. Both keys print the same four flats. Whichever chord the music closes on is the one you are in.
Numbers you can check
Equal temperament from A 4 = 440 Hz: pitch = 440 × 2((midi − 69) ÷ 12) Hz. A flat 4 is midi 68, so 440 × 2(−1 ÷ 12) = 415.305… Hz, written 415.30 Hz. F 4 is midi 65, so 440 × 2(−4 ÷ 12) = 349.228… Hz, written 349.23 Hz.
The accidental count is four, names B flat, E flat, A flat, D flat. Four perfect fifths below C spell A flat. Three semitones under A flat spell F.
The arithmetic is separate from the recording. On 20 October 2026 the key finder called Bach’s A flat major prelude opening A flat major at 46% confidence, and marked that reading low.
A recorded example you can check
Wikipedia’s The Well-Tempered Clavier article, read on 20 October 2026, lists Book 1 No. 17 as Prelude and Fugue in A flat major, BWV 862. The Open Well-Tempered Clavier score, MuseScore edition by Olivier Miquel, version 1.0 of 19 March 2015, marked Creative Commons Zero, heads the page “Praeludium 17 / BWV 862” and prints four flats between the treble clef and the time signature. The clip is the opening of that prelude. The catalog names the key. The engraving shows the four flats. Those are two documents.
On 20 October 2026 at 06:03 EDT this site’s key finder read the clip as A flat major, Camelot 4B, at 46% confidence, with the hint “Low — check by ear”. The next two candidates were E flat major (Camelot 5B, 15%) and C minor (Camelot 5A, 12%). The note on the screen said a low-confidence key, A flat major, and that E flat major also fits. The percentage is this file’s estimate, not a measured accuracy rate. The article and the score name A flat major. The finder names the same key, and it also keeps E flat major in view because 46% is low.
What our key tools tell you
The key finder names a key from a recording. Key from chords names one from chord symbols. Neither tool redraws the staff. Four flats still mean B flat, E flat, A flat, then D flat, even when a short clip is unsure between A flat major and E flat major.
4 flats key signature: quick answers
What key has 4 flats?
A flat major, and the relative minor F minor. Both use a 4 flats key signature.
What are the 4 flats in order?
B flat, E flat, A flat, D flat. The order of flats is B, E, A, D, G, C, F, and this signature stops at the fourth step.
Where does D flat sit?
On the treble staff, the fourth line. On the bass staff, the third line. It is the rightmost flat of the four.
What is the relative minor of A flat major?
F minor, three semitones under A flat. Book 1’s prelude in this signature is the A flat major one, not a separate F minor prelude.
What did the finder return?
A flat major, Camelot 4B, 46%, marked low. E flat major at 15% and C minor at 12% came next.
What this page leaves open
- Harmonic and melodic minor raise the seventh, and sometimes the sixth, above what these four flats print.
- 415.30 Hz and 349.23 Hz are equal-temperament arithmetic. They were not measured from the piano file.
- 46% describes this 20-second opening. The finder itself said the reading was low and that E flat major also fits.