[1] It is a form of modal interchange, used specifically within Turkish makam music.
As with modal interchange, it is easier to do a geçki between two similar makams.
Neva and Hüseynî share many of their features, including their notes.
A geçki can also happen through the change in the Durak (the tonic note).
While performing, if one were to flat the 6th note of Rast, they would get Basit Suzinak.