I interpret it as a reinforcement of this primary theme. The Warriors have (mostly) survived the night, only because they stuck together and had each others' backs. They made the journey to the Bronx in the first place because they believed in the power of the truce and how it could improve everyone's lives. That belief was shattered, but now that they've made it home, their journey has restored their hope for what comes next. They can continue dreaming of a day when they are living, not just surviving. The last bit of music is the Warriors doing their little chant, back home on Coney Island, which really drives home the "strength of community" message.
Having read a bit more of the background for the piece, I think there are also illusions to the birth of hip-hop and how it ultimately gave way for gangs to engage in cultural battles through music, dance, etc. and less in actual turf wars and violence. I think the last line, "This is the sound of something being born" is very much about this.