Hard Bop was birthed as an opposition to cool jazz of 1950s and was played mostly by urban musicians (from Philadelphia and Detroit) reflecting an East Coast, extroverted response to urban life.
While cool jazz preferred a light timbre, hard bop preferred a sound that was heavy, dark and impassioned. The saxophone of choice was tenor which replaced the alto and drummers played in a more assertive style.
So basically what is happening is the fact that a person is sick and it is basically written as wording in a sense to signify that.Sorry, I had to rush.Hope this helps!