This text deals with the principles of the use of microtonal intervals in northern Indian ragas and the methods of deriving the ratios between the individual degrees of the mode. These calculations are directly related to systems of just intonation in Western music. For every raga, however, the tuning system is a bit different, depending not only on the particular mode, but also on the placement of the dominant tones of the raga. What would appear to be the same note may actually have different micro-intervallic shadings (shruti) in two different ragas. Interviews with the eminent Indian musician Amit Chatterjee constitute an important source for this text.