D♭ melodic minor

D♭1E♭2F♭♭3G♭4A♭5B♭6C7

Minor third, major sixth and seventh — the ascending form, and the parent of most of the altered sounds below.

The same sounds spelled from the other side are C♯ melodic minor.

Written out

Fig. 2 · Db melodic minor, ascending

Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.

D♭WE♭HF♭WG♭WA♭WB♭WCHD♭

D♭ melodic minor is D♭, E♭, F♭, G♭, A♭, B♭ and C, and back to D♭.

Its steps are W – H – W – W – W – W – H, where W is a whole step and H a half.

It costs 6 alterations to write — near the limit of what a key signature can carry.

On the same tonic, D♭ major differs from it by exactly one note.

Found by testing every chord in the catalogue against these 7 sounds, not chosen.