EDDIE DURHAM played both slide & valve trombone. He used various types of plungers. Most of his early recordings are with both instruments. However, due to arthritis, he played less guitar and more trombone in his senior years, therefore people of different decades have the belief that he was first a guitarist and then a trombonist, but actually, he learned both instruments at the same time, as a youngster in San Marcos Texas, from his eldest brother, Joe Jr. In fact, he played brass with the Circuses, which were his earliest years of performance.
click for: JAZZIPEDIA ARTICLE
The late legendary trombonist, Al Grey, said in an interview that "he would breathe opposite the way you normally breathe, Eddie would say put it in the diaphragm and then you control it up on the lips and you can keep that pressure off your lips. This technique was later developed into circular breathing, but it was Eddie Durham's invention."
The late legendary trombonist, Benny Powell is quoted: "When you speak of non pressure system it's actually not applying pressure to your lip. The natural feeling when you want to play a higher note is to squeeze it against your lip and use pressure. What ED did was he was able to play without really tightening it up on his lips. To me he was an inventor, that's how he did all of this stuff. He invented new ways to do things, new ways to write things. That's how he maintained his range playing high notes long after times when most guys his age couldn't do that anymore" TROMBONIST, BENNY POWELL'S NEW ORLEANS FUNERAL IN NYC