What Brown wanted to do was lay down a strutting, macho anthem marked by explosions of brass and a guitar that sounds like chrome wheels spinning. He hums a melody to the sax player and a bass line to the bassist. He thumps out a beat for the drummer. He watches a trumpet player struggle, fires him, then re-hires him moments later. And when the singer is ready, he screams out a set of lyrics scratched on a sheet of paper. The song is called “Papa’s Got a Brand New Bag.”

Finding the entrance points to New York's musical undergrounds has never been quite as simple as decoding MTA maps, though that's usually the first step. Two excellent new books chart a decade-and-a-half worth of street-level detail, illuminating not only entrance points, but how they were willed into existence.