A mobile group organized by Buddhist caste communities, this ensemble plays in all sorts of religious processions, and daily in the Buddhist holy month of Gumlā. For Newar householders, there has for centuries been the general attitude that to be a complete Newar Buddhist man meant knowing how to drum.

During Gumlā, the bājan members get up every morning at sunrise and go up on the Svayambhū stūpa hilltop, where the leader organizes large group pūjā offerings, after which the ensemble assembles to play, circumambulate the great stūpa, and return back to town, visiting prominent Buddhist temples and monasteries on the route.

The members all learn to play two portable drums, the smaller nāykhī and the larger dhā. Both are played with a drumstick in the left hand and with the right hand alone, as the drum is held in place by a shoulder strap. There are large and small cymbal; the musician with the hand cymbals (tā) keeps the beat and leads. Modern western woodwind and brass instruments have been added to the Gumlā bājan in recent decades in some communities, getting away from the wooden flute accompanists once hired from the farmer community.

The tradition is so intricately developed that there are traditions for playing certain beats and songs while circumambulating the stūpa, visiting shrines around the hilltop, and then while visiting different temples along the route to town. Bājans have grown in popularity in recent decades, with young women joining as drummers in what was once a male-only practice.