Adding mass to a horn does make a difference. Sometimes the difference is to the better, and sometimes to the worse. I have done a lot of experiments with different horns, with adding mass to the mouthpieces, and to the bottom valve caps. None of these experiments have been done scientifically correct, as I have not used any equipment to measure the result. Just used my own and other peoples ears. Adding mass to the mouthpiece: As some of you might have discovered already, I have invented my own interchangeable mouthpiece sleeve system, (TRSS), which allows me to use my “converted to threaded, standard stock, off the shelf, Schilke 16 mouthpiece” with a lot of set up options. The picture shows Taylor's threaded mouthpieces. Lately I did an experiment with a “non-believer”, who is a very experienced player and conductor in the British brass band society. I used a Taylor Chicago Lite and an Olds Recording, which are two very different horns. The mp set ups were: No sleeve, brass sleeve, aluminum sleeve and aluminum/wooden sleeve. I played the same melody line, with the same effort with all the set ups with both horns. His immediate reaction was: “I don’t believe it, but I have to, because I can clearly hear the difference between the set ups. Amazing stuff”. I also did a test with my Yamaha YCR 731 cornet. Set up: No mp sleeve, brass sleeve, brass sleeve and heavy bottom cap. He was able to hear the differences clearly here too, and the best set up was with brass sleeve and heavy bottom cap on third valve! The bottom cap is massive brass, diameter 23mm and height 30mm. The most unexpected experience I have had by adding mass to a horn is when I made a prototype for a left handed flugel player from polyamide. It is made from massive polyamide with a hole drilled through the whole device. When doing some adjustments on the device, I noticed that the horn had changed to a fatter sound. The device was mounted high on the valve casing, so it shouldn’t affect much in theory, but it did….