The first time I came across the phrase 'graha bheda' was in a book called Sangeetha Darpana by Prof. Ramaratnam. For someone who exactly knew the aarohana and avarohana of three or four raagas, a detailed discussion of graha bheda, it's possibilities and limitations were too much to swallow. What? Getting Kalyani from Shankarabharana and todi?
Luckily, I had the luxury of having my grandma's old harmonium at my disposal.