It's all about the Arabic maqam, the method used in much of the music of the region. Not a chordal structure, it's more an improvisational melodic approach based on 24 tone equal temperament. Or 17 equal temperament. There's others, too. It gets very confusing.
The headless instrument is a saz, aka bağlama, great fun to play. If you fancy something different I'd recommend getting one. Such a wonderfully versatile instrument.