Sentence:  The rougher bands, like Kid Ory&#39;s or Frankie Dusen&#39;s Eagle Band, thrived; they were the “<WSD>routiners</WSD>,” the improvisers who worked from their ear rather than reading music. 
Meaning of the word marked with <WSD> tags:  A jazz musician who plays by ear (i.e. not using sheet music, but rather following along with the band and memorizing music when needed).