C#9 arpeggio for gypsy jazz
The C#9 arpeggio is built from the notes C# (R), F (3), A♭ (5), B (♭7), E♭ (2). On Haute Gitanerie you can see it across the whole guitar neck — contained position boxes, long diagonal forms, and its parent scale (C# Mixolydian) — with note names in English (C D E) or solfège (Do Ré Mi).
How to practise the C#9 arpeggio
Start with a contained position box near the low strings, then move it up the neck fret by fret, or follow a diagonal form for a two-octave sweep in the manouche style. Every note is labelled with its interval (R, 3, 5, ♭7, 2), so you always know where the root, third, fifth and seventh sit.