When you first hear about the huge number of raags in Indian classical music, it can feel overwhelming. To bring some order to this universe, musicologist Pt. Vishnu Narayan Bhatkhande proposed a system of ten basic thaats â€“ parent scales from which raags are derived. A thaat is a specific arrangement of the seven swars within an octave. In Western terms, you can think of thaats as something like â€œmodesâ€ or â€œparent scalesâ€, while raags are more like specific melodies and characters derived from those modes. The ten thaats are commonly listed as: <ol> <li>Bilawal</li> <li>Kalyan</li> <li>Khamaj</li> <li>Bhairav</li> <li>Poorvi</li> <li>Marwa</li> <li>Kafi</li> <li>Asavari</li> <li>Bhairavi</li> <li>Todi</li> </ol> <h3>Rules of a thaat</h3> <ul> <li> A thaat must contain seven notes (Sa Re Ga Ma Pa Dha Ni) in some combination of shuddha (natural), komal (flat), and teevra (sharp). </li> <li> It is defined in a simple ascending order â€“ just a clean list of notes, no ornamentation, no zigzags. </li> <li> Thaats are not performed in concerts. They are theoretical frameworks; it is the raags that are actually sung and played. </li> <li> Many thaats are named after a key raag from that group (e.g., Bhairavi thaat from Raag Bhairavi). </li> </ul> For example, if you know Western modes: Bilawal thaat is similar to the major scale (Ionian), while Kafi thaat has a flavor somewhat like Dorian. However, raags built on these thaats can be drastically different from Western melodies because of their rules, ornamentation, and time-of-day associations. The thaat system is not a perfect representation of every subtlety in Indian classical music, but it remains a powerful teaching and cataloging tool, especially for beginners and for organizing large raag lists.