A lot of people seek to know about swarodaya. You can never learn it from books. Most people want to learn about it to get success in material life – including wealth, romance, power, success etc.
A guru knows about it but he can only reveal it to those who only seek the love of God and not material success.
Thus the truth of swarodaya is kept hidden
Vivekananda described a few small things and Yogananda has described a few minor details – such as flow through left nostril gives success etc. HOWEVER, the truth is much deeper. Even the books only gave a very superficial knowledge. In the book shiv swarodaya, the author described time and length of swar, the association with certain tattva, – yet the real core was kept totally hidden.
All books and upanishads, Gita, bible, Torah were written with a deeper meaning. Even the simplest of simple statements have a very deep meaning. For example, the word swarodaya itself – at a deeper level has nothing to do with flow of prana through nostril but something much deeper
Bhavin