Excerpt from my book The Theory of Rebetiko: From the Makams of Asia Minor to the Dromi of Piraeus.
Nikriz Mode
The Nikriz mode has its theoretical basis and final on C, where the fundamental element 5x-nikriz is based, giving the mode its name. This mode is not characterized by any specific incipit. The elemental structure is completed with a 4x-rast on G. The extension is possible with a 4x-chitzaz (less commonly, with a 4x-rast) on low G, making low B 1 comma flat the sub-final of the mode.
The modal dominant is G. The attraction B 1 comma flat↝Bb is nearly systematic in descending phrases and in phrases that do not extend over high C. A characteristic feature of Nikriz is the temporary lowering of F# to F when phrases emphasize the IV degree.
Dromos Nikriz
The adjustment to equal temperament is referred to as dromos Nikriz or equal-tempered Nikriz mode (or Nikriz*) and occurs as illustrated in the following figure. All the characteristics of the corresponding microtonal mode are preserved.
