From Gypsy Jazz Guitar Wiki
Another aspect that is really typical of Manouche style, it's their way of building chords, and especially the way they often use the 6th and frequently the 9th. With 6th chords and a goiod sens of rhythm for the pompe, we can have some good fun. However, people starting Manouche who have already been playing guitar for a while will have to forget about those barrÃ© chords and use the jazz fingerings. For the jazz guitarist, the transition will be smoother but there will probably be a bit of work to switch over from 7th and domninant 7th chords to 6th chords.