The music is meant to help the community grieve and "move forward," Hallmon said.
The group's musicians are on-call during designated Saturday nights, when they must be ready to assemble anywhere in the city.
Feedback has so far been positive, Hallmon said. The first time the ensemble performed after a shooting, a woman introduced herself to Hallmon as the mother of the shooting victim.
"I will sleep better tonight knowing you are here," she said, according to Hallmon.
The group tweets the time and location of upcoming shows on its Twitter page.