Maybe she's trying to get the same amount of sound out of the muted instrument and is forcing it. You do have to adjust air pressure and lip a bit when you have a mute in - especially the cone mute that is often used for students (as opposed to bell mute)


>>>Ok, all you musicians out there. A mute should not change how the tone of a note sounds, just how loud. Right? We have a promising Alison Balsom here and when we put the mute in her trumpet, the notes tend to break and are not clean. I tried it as well with the same result. Take the mute out and they are good. It's a Humes & Berg student mute, if that matters. The corks are filed down much, but seems to be plenty of room for air to get through. I think the trumpet is a King (she's practicing now). Any ideas?
>>
>>Brings back memories. Used to play a King and man I loved my mute. Do you mean the tone or the pitch? I think the tonal quality definitely changes - that's part of the idea of the mute - gives it kind of a funky, less brassy sound. Pitch shouldn't change at all. Listen to some old Harry James or Biederbecke when they use the mute.
>
>The notes actual crack and break. I think Alan may be onto something with the air being restricted. I'm going to look into other mutes that soften/mellow the tone.
>
>I thought it was amazing that I haven't picked-up a brass instrument in over 30 years, but I still remembered the scale. It's probably why I can't find my glasses half the time; no more room in the keppie!