The dhol is a double-headed barrel drum carried on a strap, struck with a heavy bent stick on the bass side and a thin cane on the treble. It is the loudest thing in a Punjabi village and it is used to gather people, not only to accompany them.
Dhol rhythms have names and functions: bhangra, jhummar, luddi, dhamal, kaharwa. A dholi announced, called to a wedding, drove a wrestling bout and led a procession.
The players were traditionally from the mirasi community, Muslim musicians who also kept genealogies and sang at family occasions, and who were paid in grain and gifts rather than fees.
In 1947 the mirasis left Indian Punjab almost entirely. What that removed from the musical life of Sikh and Hindu villages has never been properly assessed, and the same is true in reverse for the Muslim villages that lost their Hindu and Sikh musicians.
The dhol survived because everyone wanted it. It is now amplified, played at weddings by professionals from anywhere, and is the single most recognisable sound of Punjab in the world.
The shell is mango or sheesham, hollowed and turned, the heads are goat on one side and buffalo on the other, and the tension is taken on a rope lacing beaten tighter with a block of wood before a performance. It goes out of tune with the weather and is tuned by being hit.
Bhangra as a stage form was put together in the 1950s out of harvest dances from the Sialkot and Gujranwala country, set on a proscenium for the Republic Day parade and the state's festivals, and given a fixed drum part and a fixed costume. The dances it was made from had no fixed anything.
It went out with the emigration and went further than the people did. Players work weddings in Southall, Brampton and Melbourne, the drum is taught in British schools, and it turns up now in music with no connection to Punjab at all.
Ethnomusicological literature on the dhol and on mirasi musicians.