Does anyone else here play on a bobby shew jazz mouthpiece? It's the yamaha one which is similar to a 3c. I have been playing it regularly recently and can't quite get my head around it. I love the sound I get from it but i have to really fight to keep in tune between 3rd space C and the F# above that. Tuning is fine throughout the rest of my usable range up to F above high C. Any ideas what could be causing this?

What horn are you playing?

Measure your gap.(distance between shank end of MP and the lip at the end of your receiver). I will bet it is way too small or big.

v

I thought about that as well but it seems to be the same on both my horns and my friends pocket trumpet! I play a Holton t102 and a 8310z

I was thinking it could be the backbore as I used to play on a 3c and it does feel quite different.

I would keep at it. What is happening in the range where you are having issues - flat or sharp (or both)?

The notes are flat. I think it may well just be that I have to take more time to adjust to the change from the 3c.