Volume control with external synthesizers
The topic here is volume control when MuseScore is playing through an external synthesizer (presumably one that conforms to the General MIDI specification).
A widely recommended protocol for volume control in that context is:
• MIDI Control Change 7 (CC7 - "Volume") is sent at the start of play. This establishes the "overall volume" for the part. We can change the value of this message among the different parts to "balance" the instruments.
• MIDI Control Change 11 (CC11 - "Expression") is sent to implement dynamic indications on the score, such as dynamic marks, hairpins, and the like.
• Note-to-note volume variations, such as to impart certain musical subtleties "in performance", or resulting from the original construction of the score by the recording of a human performance on a keyboard, are conveyed in the MIDI stream by the velocity values of the Note ON messages.
Can we arrange to follow this protocol in the playing of a score by MuseScore through an external synthesizer? Yes. To do so:
Have the velocity type of all notes in the score be "User". (That means that these are the "absolute" velocities of the notes, not intended to by modulated by the current dynamic state.) If we don't plan to have note-to-note volume variations, all note velocities should be set to a consistent value, perhaps 80.
In the Synthesizer panel, the Dynamics tab, have Dynamics Method set to either "Default (single-note dynamics and velocity)" or "CC events only (constant velocity)".
In that same tab, have CC to Use set to "CC11".
In Mixer, be sure that the Sound ("patch") is not set to an "Expr." ("Expressive") selection. (If it is, MuseScore will send the bank selection as "17", which might baffle the external synthesizer. That bank selection is for the benefit of the "Internal" synthesizer, which has special properties in its "Expressive" mode.)