According to traditional books of Indian Classical Music designation of vadi swar in a raag is like a king in a kingdom. Usage of vadi swar is more then any other swar in a raag. Speciality of any raag is depend on vadi swar because of this vadi swar is also called as ‘Jeev swar ‘or ‘ansh swar’. A good artist uses vadi swar in different ways like singing vadi swar again and again, sarting a raag with vadi swar, to end a raag with vadi swar, singing vadi swar many times in important places with different-different swaras or sometime singing vadi swar for longer time in one breath.
Vaid swar is also helpful to identify the time of singing or playing a raag. If vadi swar of a raag is from purvang part of saptak i.e. “Sa Re Ga Ma”, then it is called as purvang vadi raag and usually time for singing or playing purvang vadi raagas are from 12 pm to 12 am for example raagas like Bhimpalasi, Pilu, Purvi, Marwa, Yaman, Bhoopal, and Bageshree etc. have purvang vadi swar and so the time for singing and playing these raagas is between 12 pm to 12 am.
In the same way if vadi swar of a raag is from utrang part of spatak i.e. “Pa Dha Ni” then it is called as utrang vadi raag and time for singing or playing utrang vadi raagas is from 12 am to 12 pm. For example raagas like Bhairav, Bhairavi, Bilawal, Kalingada, Sohini, and Asavari etc. have utrang vadi swar and so the time for singing or playing these raagas is between 12 am to 12 pm.
Vadi swar has one more significance that if only vadi swar is changed in a raag then it also changes a raag weather the swaras of raagas are almost same. For example raag Bhimpalasi, and raag Dhanashree, these two raagas come from the same thaat i.e. thaat kafi, and in both the raagas komal “Ga-Ni” are used but when raag bhimpalasi is sung or played then swar Ma is shown many times because it is a vadi swar of raag Bhimpalasi and when raag Dhanashree is sung or played swar Pa is seen more because swar Pa is vadi swar of raag Dhanashree. Thus it is concluded that if only vadi swar is changed in a raag then raag is also changed.