Neville, greetings and no comedy intended
A BERP or "the buzz extension & resistance piece" is a reality
It is sold and distributed by Musical Enterprises,PO Box 1041 Larkspur, Ca. 94977-1041
The BERP is an invention of Mario Guarneri. The following is stolen from one of the flyers.
In a book "Brass Basics & The BERP" Guarneri focuses on breathing and air stream exercises, embouchure formation, and strengthening, ear training, range and articulation with the BERP and gives examples. I have found that the BERP is an excellent tool and working with the muscles from a kinetic perspective, and I find that its greatest advantage comes when using it to work on ear-training.
The way it works is that your mouthpiece slips into its receiver and then it fits into your trumpets receiver. It diverts the air away from the horn and prevents it from going down the leadpipe. While just blowing into your mpc you have no resistance through the BERP you get that. No chance of setting up a standing wave pattern though as with the leadpipe. Then what you are supposed to do is play an etude You depress the valves just like you would if you were playing through your horn but instead all the sound you get is a mpc buzz. Something about the usage of your fingers while buzzing is supposed to kinetically lock in tones and you can play an etude much more effectively than trying to buzz one on just your mpc.
If you've never experienced it, it will sound a little goofy but after experiencing I can admit that there is a lot to be gained. I wouldn't use it as an exclusive tool but it definitely could be one of those advantages that helps one break through plateaus in growth.
If you get a chance give one a try.