Geçki

Geçki is the usage of a different makam during the performance of another makam, which may or may not lead to a modulation. It is a form of modal interchange, used specifically within Turkish makam music.

Music theory
As with modal interchange, it is easier to do a geçki between two similar makams. There are two forms of geçki, the ones that create a change in function and the ones that create a change in identity. These two forms of geçki can be used simultaneously.

Change in function
A geçki can happen without changing any notes by changing the roles of the notes within a makam. Neva and Hüseynî share many of their features, including their notes. However, Neva has its Güçlü in its fourth note, while Hüseynî has its Güçlü in its fifth note. So performing the fifth note as a Güçlü while performing the Neva makam is an example of a Hüseynî geçki within a Neva makam.

A geçki can also happen through the change in the Durak (the tonic note). The Rast makam can be reached by making the Yeden (the leading tone) of the Uşşak makam into the current Durak. This is because the lower pentachord of Rast functions as a mode of the lower tetrachord (including the Yeden) of Uşşak.

A visualisation of how the geçki between Hicaz and Nikriz would work can be seen below. Changing the Durak note from the 1st to the 2nd note (or vice-versa) would be a geçki between these makams.

Change in identity
Geçki can also happen through changing a note in a makam and thereby modulating it into a different makam. This change is usually done through the use of accidentals.

An example of this is a geçki between Rast and Basit Suzinak. While performing, if one were to flat the 6th note of Rast, they would get Basit Suzinak.