Interestingly, while playing instrumental music the smallest ‘discernible interval of pure sound’ is again termed shruti .They are 22 in number. This is the finest scale of tones that can be comfortably played on the stringed instruments. One of these instruments is the dhruva veena, an instrument with 22 strings, which is the reference standard of the Indian music system. For, dhruva means ‘constant’ and is also the name of the ‘north-star’. The Carnatic music system of south-India still adheres to the shruti system for its daily vocal rendering.
All the present day ragas are based on the selection of 7, 6 or 5 notes out of these 12 notes. And in an Indian classical music composition you can go up the scale in one raga and come down the scale in another. This is termed as the aroha and the avaroha respectively. This gives us the possibility of hundreds of thousands of combinations – the ragas therefore change with the season, the time of day, location and so on. The multiplicity of the world around us reflects comfortably within this structure of the ragas and those who sing the Divine song are thus called the raagis .