Hello Herman, OK, the answer to your question would be yes, the “Bell” or “flare” of the trumpet would contribute a significant change in the tone. The Design of the melodica would require as you stated that the sound be gathered in one section and then pass through a tube and exit through the Bell. The tone of the instrument is created in the body (Tube) and like a Trumpet when the sound exits the bell, there would be a modulation of the tone. If the bell is large the tone would then change to a darker or mellow tone. If the bell is smaller in size the tone would be a brighter sound. Since the actual pitch of a melodica is created by the reed, the only way the pitch would change would be through manipulation of the reed to create a variation in the pitch. The tube would not create a change in pitch as it would in a trumpet via the throat of the mouthpiece and the length of the tube. The question regarding “Mute” can be achieved, but the sound cannot escape the body of the melodica before it exits the bell. At this point the sound would be able to be modified like when a mute is used on a trumpet or in an open/closed motion to create a Wow effect. I guess the last thing would be for me to provide an example of such a creation.
Here you go