These musical elements are organized into scales ("mela"), and the South Indian system of "rāga" works with 72 scales, as first discussed by "Caturdandi prakashika". They are divided into two groups, "purvanga" and "uttaranga", depending on the nature of the lower tetrachord. The "anga" itself has six cycles ("cakra"), where the "purvanga" or lower tetrachord is anchored, while there are six permutations of "uttaranga" suggested to the artist. After this system was developed, the Indian classical music scholars have developed additional "rāgas" for all the scales. The North Indian style is closer to the Western diatonic modes, and built upon the foundation developed by Vishnu Narayan Bhatkhande using ten "Thaat": "kalyan, bilaval, khamaj, kafi, asavari, bhairavi, bhairav, purvi, marva and todi". Some "rāgas" are common to both systems and have same names, such as "kalyan" performed by either is recognizably the same. Some "rāgas" are common to both systems but have different names, such as "malkos" of Hindustani system is recognizably the same as "hindolam" of Carnatic system. However, some "rāgas" are named the same in the two systems, but they are different, such as "todi".