[Melodica-Me]

Hello Herman, The sound does not change using a Trumpet or French Horn mouthpiece, using a standard trumpet mouthpiece piece requires that you bore out the throat to allow more air to pass through to the backbore. If the hole remains the same, the amount of air will reduce the actual volume produced by the melodica. Once you bore the mouthpiece, it will no longer work as a traditional trumpet mouthpiece and will no longer work on a trumpet. The reason I like a trumpet mouthpiece is that I am able to play staccato with much more ease and faster than if I am to use a straight piece or a duck bill mouthpiece. The first mouthpiece I bored out was a French horn mouth piece for my Vibrandoneon. Note I also changed the reciever to allow for the use of this type of mouthpiece, you can see here https://i.pinimg.com/originals/8d/0f/b3/8d0fb311a53bcbb7df761e3ac0b4b43f.jpg. I kept this design and incorporated it with my Diamante Wind Vox Melodicas https://i.pinimg.com/originals/eb/1f/5b/eb1f5b6dcaacdf91fb767b8e42275311.jpg.
I hope this helps with your question.
Melodica-Me