This is a nice triadic idea that works through a dimished scale. By simply playing 2nd inversion major triads down by minor thirds you get a nice melodic line that clearly outlines the 4 major triads found in diminshed harmony.
This line also works nice over a dominant 7th chord with a #9, b9, #11, 13. Or over a standard diminished chord. Since it is so symmetrical, it will work nicely for playing outside the changes as well…
The line is played around the circle of 4ths starting on concert C. After you feel comfortable with the melody, practice improvising with the underlying structure (major triads descending by minor 3rd). Using this basic schematic, you can discover endless melodies.