This book is part of a series composed of 4 books: “Measures in Music”, “Intervals in Temperament & Arel-Ezgi Systems”, “Scales, Modes & Maqam Scales” and “Chords & Fourth Harmony Chords”. In this study, we tried to disclose as much briefly as possible the definition, naming and features of intervals in two music systems. Moreover, we prepared the listening samples of intervals in 2 music systems. Audio files are distributed with the book via Internet. The readers would also find in the text the notes of all of these listening samples. Therefore, readers would not only be able to learn the theoretical dimensions of the intervals but also to examine a set of intervals via listening to them in all tones.