One of the most informative U Tube things is the How it's made one on making French horns. They use a form of pitch( pun not intended) instead of an alloy which melts at 70C from Fry's Metals. It's in one of my late wife's huge library on music.
However, the video which I clear ly like is how to remove dents and kinks in tubing by forcing a number of correct diameter ball bearings into the damaged tube.