The esraj (Bengali: এস্রাজ; also called israj) is a string instrument found in two forms throughout the north, central, and east regions of India. It is a young instrument by Indian terms, being only about 200 years old. The dilruba is found in the north, where it is used in religious music and light classical songs in the urban areas. Its name is translated as "robber of the heart." The esraj is found in the east and central areas, particularly Bengal, as well as Bangladesh, and it is used in a somewhat wider variety of musical styles than is the dilruba.
The Dilruba originates from the Taus and some argue is the work of the 10th Sikh Guru, Guru Gobind Singh, whilst that of the Taus was the work of Guru Hargobind (the sixth guru of the Sikhs). The Dilruba was then produced to replace the previously heavy instrument (the Taus). This attempt was intended to 'scale down' the Taus into what is now known to be the Dilruba. This made it more convenient for the Sikh army to carry the instrument on horseback.
The structure of both instruments is very similar, each having a medium sized sitar-like neck with 20 heavy metal frets. This neck holds on a long wooden rack of 12-15 sympathetic strings. While the dilruba has more sympathetic strings and a differently shaped body than the esraj, they both have four main strings which are bowed. All strings are metal. The soundboard is a stretched piece of goatskin similar to what is found on a sarangi. Sometimes the instrument has a gourd affixed to the top for balance or for tone enhancement.
The instrument can be rested between the knees while the player kneels, or more commonly rested on the knee of the player while sitting, or also on the floor just in front of the player, with the neck leaning on the left shoulder. It is played with a bow, with the other hand moving along the strings above the frets. The player may slide the note up or down to achieve the portamento, or meend, characteristic of Indian music.
The esraj is mostly used as an accompanying instrument. It is the accompanying instrument of choice for Rabindra Sangeet singing. However, it has also been used as a solo instrument to interpret Hindustani Classical Music, mostly in the Vishnupur tradition. Additionally, the esrag is a more modern invention from the Dilruba that was made and promoted by the Namdharis.
Both the dilruba and the esraj had been declining in popularity for many decades. By the 1980's the instrument was nearly extinct. However with the rising influence of the "Gurmat Sangeet" movement, these instruments are once again attracting considerable attention.