Ab bb c db eb f g Ab
1 2 3∼4 5 6 7∼8
The fourth of Ab is db and has five flats:—
Db eb f gb ab bb c Db
1 2 3∼4 5 6 7∼ 8
The fourth of Db is gb and has six flats:—
Gb ab bb cb db eb f Gb
1 2 3∼4 5 6 7∼8
The fourth of Gb is cb and has seven flats:—
Cb db eb fb gb ab bb Cb
1 2 3∼4 5 6 7∼ 8
The fourth of Cb is fb and has eight flats. This key necessitates one double flat and b has the double flat. The double flats are added in the same order that the single flats are. The double flat (designated: bb) lowers a tone one whole step.
Fb gb ab bbb cb db eb Fb
1 2 3∼4 5 6 7∼ 8