The usual trumpet player will have a puddle of water under his shoes by the end of the performance, which makes his steps extra slippery and an increased risk of fall and injury. More… Trumpet Hub
Nobody ever explains why this is. Nobody ever takes the time to offer explanation as to why a brass player will occasionally reach forward to the tuning slide and press a small trigger.
Is it taboo? Are we not allowed to mention such a thing? Hmmm…?
It is let the saliva out.
As we blow, a little bit of spit goes in. At some point, it has to be released or the sound produced becomes gargled, much like your morning routine with mouthwash. And that saliva ends up on the floor, just in front of your feet.