The twelve signs therefore, are divided and sub-divided in different fractions, the sequence of which gets repeated after every twelve divisions. Each cycle of twelve divisions represent a ‘harmonic’ depicting the various levels of consciousness, both gross and subtle, which exists in the life of a person. The first cycle of divisional charts from D-1 to D-12 represent the physical plane. They cover the various aspects of the physical realities of a person such as the body itself (D-1, Rāśi), wealth (D-2, Horā), co-born or siblings (D-3, Drekkāṇa), properties and fortune (D-4, Chaturthāṁśa), progeny (D-7, Saptāṁśa), spouse (D-9, Navāṁśa), profession, career and work (D-10, Daśāṁśa) and parents (D-12, Dvādaśāṁśa). Of these, the Rāśi (D-1), Drekkāṇa (D-3) and Navāṁśa (D-9) are considered to be the most important in analyzing a horoscope.
The next cycle is the first harmonic of the previous cycle, covering divisions from D-13 to D-24. This represents the conscious plane, depicting the various existential conditions of a person. Although technically 12 divisions are possible in each cycle, Parāśara’s format of ṣoḍaṣavarga or the 16 kinds of divisions of each sign is being followed here. In this format, the three divisions of Kālāṁśa (D-16), Viṁśāṁśa (D-20) and Chaturviṁśāṁśa or Siddhāṁśa (D-24) are generally used, as the primary divisions to be studied in this cycle. Kālāṁśa is the first harmonic of the Chaturthāṁśa showing luxuries, vehicles and mental happiness. Viṁśāṁśa deals with the spiritual life of a person while Chaturviṁśāṁśa deals with higher learning. This cycle therefore refers to the higher existential activities of a person after crossing the first rung of gross material conditions.
The third cycle or the second harmonic, covering D-25 to D-36, relates to the sub-conscious plain. These explore the factors, which lie in the sub-conscious region and unconsciously influence the mind. They represent inherent weaknesses and strengths (D-27, Nakṣatrāṁśa) and all forms of evils that might besiege a person (D-30, Triṁśāṁśa).
The fourth cycle or third harmonic ranging from D-37 to D-48 deals with past karma, which is inherited as ancestral legacy. The important divisions in this cycle are D-40 or Khavedāṁśa representing matrilineal legacy and D-45 or Akṣavedāṁśa representing patrilineal legacy. This is the super-conscious plane.
The final harmonic is that of the supra-conscious plane from D-49 to D-60. This shows the accumulated karma from past births, which a person carries with him like a legacy. In this context Ṣaṣṭiāṁśa or D-60 is the most relevant division.