Hi all, At the present time we're doing a study looking at intonation. The concept deals with sound waves and how they either reinforce(constructive) or cancel(destructive) each other out when the sound comes from two different sources. Here's what to do if you want to check it out: 1) get two trumpet players that can play in tune and warm up. 2) both play a tuning note while standing about 4 to 6 feet apart 3)while playing the notes together, start to balance the volume. Balanced volume will be when you can not hear one trumpet over the other. 4)Here's the idea, if the intonation is perfect, and the volume of the two trumpets are perfectly balanced, an intresting phenomenon should happen. 5) You can look at the bell of your trumpet and hear or feel the sensation that the other persons trumpet sound coming through YOUR trumpet. A way of to think of it is "when I play my trumpet exactly in tune and in perfect balance, the other guys trumpet sound is able to get inside my sound". It's not easy and it takes serious listening but if you have the time, let me know what you hear. We've tried it on individuals with clinically measured perfect pitch and they sense the phenomenon. Have fun and let me know what you hear.