Note preview with certain synthesizer settings sets channel volume lower
Impressively, there is a way to use single-note dynamics within Musescore even without the use of special expressive soundfonts. To do so, you go to the Synthesizer, the "Dynamics" tab, change the Dynamics method to "CC events only" and the CC to use to "CC 11" - this makes it so that crescendos and such edit the automation of CC 11, expression. Quite handy since it works with a lot of soundfonts.
However, a bug occurs if you preview a note. This includes:
- Clicking on the note
- Entering a note via note input
The volume of the entire channel is lowered. This does mean the entire instrument in that connected staves are affected, but not such that different instrument "channels" (i.e. arco v. pizzicato strings) are affected at the same time. The mixer settings remain unaffected, and while they still work the overall volume of the channel is permanently lowered. The effect persists through everything from soundfont changes to closing/reopening the score, and is only reset by exiting Musescore and restarting. Exporting the audio exports the instruments at the correct volume.
So saving the score doesn't save this strange permanent volume change between sessions, meaning something happens in the short-term when previewing notes that lowers the volume of the channel that isn't reset upon exiting the preview state, resulting in lowered volume during playback.