The ten thaats, and what they do not tell you

What a thaat is

A thaat is a scale of seven swaras — one form of each — used to file raags. V.N. Bhatkhande settled on ten of them early in the twentieth century, and almost every book and syllabus since has used his scheme.

The ten: Bilawal, Khamaj, Kafi, Asavari, Bhairavi, Bhairav, Kalyan, Marwa, Purvi, Todi. Bilawal is the all-natural scale. Kalyan raises Ma. Khamaj flattens Ni, Kafi adds flat Ga, Asavari flat Dha, Bhairavi flattens everything flattenable. Bhairav takes flat Re and flat Dha with a natural Ga. Marwa, Purvi and Todi gather the sharp Ma against various flattened degrees.

What it tells you

Which notes are available, and that is genuinely useful. If you know a raag is Kafi thaat you know to expect komal Ga and komal Ni, and your hand will go to the right places before your ear catches up.

It also sorts the library. Ten drawers is a workable number, and a student who has learned one raag from each thaat has met most of the intervals the system uses.

What it does not tell you

Almost everything that makes a raag that raag. Two raags can sit in the same thaat and share every note and still be nothing alike — because a raag is not a scale.

Darbari Kanada and Jaunpuri are both Asavari thaat. The same seven swaras. What separates them is that Darbari's komal Ga is not held still: it is shaken, slowly, a wide oscillation you cannot write down, and a singer who steadies it has left the raag. Jaunpuri takes that same note straight. The scale cannot see the difference; the ear cannot miss it.

The same goes for Bhairav and Kalingada, which share a thaat and even a parent name, and are told apart mainly by pace. Or Yaman and Yaman Kalyan, which differ by whether a single natural Ma is allowed as a passing touch on the way down. One note, and the schools have argued about it for a century.

A thaat tells you which notes are in the room. It tells you nothing about which of them is being avoided, which is leaned on, which is bent, and in what order they are allowed to arrive.

Ten is a decision, not a fact

Bhatkhande chose ten. He could have chosen differently, and others did. The Carnatic system of the south uses seventy-two melakarta scales, generated systematically, which covers every possibility and files nothing by habit.

Ten thaats do not cover every Hindustani raag cleanly either. Several well-known raags fit awkwardly or belong to more than one, and the system quietly assigns them where they cause least trouble. Lalit is the usual example — it has both forms of Ma and no Pa at all, which no thaat anticipated.

None of that makes the scheme bad. It makes it what it is: a filing system invented by one scholar for teaching, adopted because it worked, and treated by some since as though it were a law of nature.