C♯ melodic minor

C♯1D♯2E♭3F♯4G♯5A♯6B♯7

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 D♭ melodic minor.

Written out

Fig. 2 · C# 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.

C♯WD♯HEWF♯WG♯WA♯WB♯HC♯

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

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, C♯ major differs from it by exactly one note.

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