Oops - wrong button,

so to clarify the above post, let us consider a chord sequence of B7 to E7 to Amaj7.

An accompanist on trombone might, in order to take the smoothest line, move from the 7th of B7 (A) to the 3rd of E7 (G#) and end on the 7th of Amaj7 (G#).

As you can see, he has only moved downwards by a semitone in the chord progression.

When you listen to New Orleans Jazz you hear a lot of chromatic movement of this sort in the accompanying instruments. The bass is usually much more lively.

The counterpoint can get more complex, but the basic idea is as shown in the example above.

To do this kind of harmony, you need to know how chords conect to each other, you have to know which notes the root, the 3rd and the 7th of any given chord are and you have to be looking ahead at the next chord and choosing which note to move to next so as to keep the texture smooth.

It should also be clarified that this knowledge and approach to harmony, though generally associated with bach was not created by him. It developed over a very long time, beginning in medieval times and growing in complexity through rennaissance and baroque times.

So to suggest that it just happened by accident one day in new orleans without prior knowledge would be like saying that einstein just happened to come up with the theory of relativity one day. The truth is that in order to do so he would have had to come up with all of Newtons and Curies discoveries all by himself first too.

We know this didn't happen. He knew and understood the work that went before him and developed upon it in new and exciting ways.

And thats what happened in America. Counterpoint became a group endevour rather than a composers challenge.