Dhatus in Musical Structure of Dhrupad
A Dhrupad composition has four Dhatus viz. Sthayi, Antara, Sanchari and Abhoga. In earlier times, Dhrupads had only three Dhatus viz. Udgraha, Antara and Abhoga. It was in the late 18th century that Udgraha Dhatu was replaced by Sthayi. The word Sthayi means constant, fixed or basic. In singing the Dhrupad composition the singer, after completing each Dhatu, returns once again to the Sthayi (Dhatu) (the first component of Dhrupad). In this way the Sthayi forms a kind of a base Dhatu. In Sthayi (Dhatu) the notes are generally sung in the lower register and lower part of the middle register.
The second component is called Antara. The Antara Dhatu made its appearance for the first time in Salaga Suda Prabandhas. The word Antara means 'different'.' This Dhatu was called Antara because it was different from the other Dhatus of Salaga Suda Prabandhas. It is generally sung in the notes of the upper part of the middle register and the lower part of the upper register.
The third Dhatu of Dhrupad is Sanchari. This Dhatu is a development of more recent times presumably towards the end of the 19th century. This Dhatu was too long and it was difficult for the singer to sing it in one piece. To make for convenience it was therefore split into two parts. The first of these was called Sanchari while the term Abhoga continued to be applied to the second part. The word Sanchari means 'flowing' or 'freely moving'. This Dhatu is called Sanchari because here the singer has the liberty of singing in any register and can easily move from the lowest to the highest register.
The last of the four Dhatus is Abhoga. The word Abhoga means 'completion'. This piece conventionally contains the name of the composer or his patron who is eulogised. Like Sanchari the Abhoga makes use of the full range of notes from all the registers.
Structure of Dhrupad Compositions
The Dhrupad compositions are structured on the framework of Prabandhas, which are musical compositions. Prabandha is made up of many melodic components known as Dhatu. Prabandha has four Dhatus though there are Prabandhas which have only three or two Dhatus. The four Dhatus are Udgraha, Melapaka, Dhruva and Abhoga. Besides these Dhatus a Prabandha has six angas (literally limbs but here in the sense of attributes). They are Svara, Viruda, Tena, Pada, Pata and text.