a. Thaat system as is well-known, was created / established by Pandit Bhatkhande ji. It has been acknowledged that he contributed greatly to the cause of Indian music through his collective efforts to standardize both the content and nomenclature of the prevailing ragas.
In my opinion, thaat system is essentially meant for a general understanding of categorisation of ragas divided into 10 thaats. However there are exceptions. There could be some examples of fitting ragas like Madhuwanti in one of the thaats. I recollect very well that in olden days a sarangi player would ask the main vocalist ‘in which thaat he should tune his instrument’. This implies that prevalent definition of a thaat was related to the scale of a raga.
To conclude, I would recommend that it is good to know details about the thaat system and the classification of the ragas according to the same. However, the focus should be on individual ragas – and individual ragas only, and not on the thaat to which the concerned raga belongs according to Bhatkhande ji’s classification.
b. Vadi/samvadi concept: whilst this concept may be of some value to the students of music, it is useful to know the basis, to start with. However, my assessment is that whilst a musician is developing a raga – especially in the alap, he/she does not give greater importance or emphasis to the vadi note of the concerned raga as compared to the samvadi note. Some of the musicians are not bothered about thaat of the raga, they just develop the raga according to their taleem. Such taleem that I referred to, translates itself into resting on significant notes whilst developing a raga. Ustads used to call such notes as ठहरनेकी जगह . I would like to call them melodic centres. Each centre has its own value, neither lesser nor greater than the other. There could be more than 2 centres in ragas like Yaman, where we have Gandhar, Pancham and Nishad as resting points (ठहरनेकी जगह) or melodic centres.
c. Aroha / avroha: as explained earlier, the concept of aroha / avroha is essentially meant for students of music. Just as the chaste language, over a period, changes itself in to a colloquial language, so also aroha / avroha concepts change into what we call as chalan. Not only that chalan partially simplifies the concept of aroha/ avroha but is used by musicians to have calculated freedom from the strict tenets of aroha/ avroha concepts. In my opinion, musicians who follow aroha /avroha strictly would be called “kitabi gavaye (bookish musicians)”.