The grouping of vowels and consonants is called Swaras and Vyanjanas respectively and is done according to the phonetic point of articulation.
Indian phonography is vowel dominant; each vowel is realizable in 3 scales Short, Long, Prolonged. All vowels can be pronounced in non-nasal and nasal modes. Which means each vowel can have 18 realizations (three divisions on the position of the particular organ in the mouth while pronouncing that letter, and two divisions of nasal or non-nasal. Since each group is independent of the others, the total number of pronouncements comes to 18). Since it is not possible to record these differences and they must be remembered by listening to it properly, the Vedas were not written.
For representing all these differences there must be a provision to apply vowels hence there are Vowel-marks called as Matras. There is only one three vowel combination that is Om.
All consonantal designs either touch or cross the vertibar; there are exceptions only in the design of letters such as GA, NA, SHA. These letters do not touch the vertibar. This is a graphic peculiarity to point to the fact that the writing is a Ganesh Vidya.
According to the tradition of the scribes of the Ganapati School, one scribe came to write the copies text of Mahabharata for the author Vyasa Muni. Ganesha introduced vertibar of ‘A’ vowel. This feature is high-lighted by Vyasa in Bhagwad Gita wherein Krishna says, ‘I am the common factor of Aa kaar in all letters.’ Thus this feature was added in all consonantal designs. After the vertibar is drawn predominantly the graphics becomes ‘Dev-Lipi’.