Velocity
One further clarification, when I select a note in a score (a melodic instrument) and the note has a dynamic symbol attached, in the Inspector Window in the Note category I sometimes see the Velocity value correctly indicating the Dynamic (in this case Dynamic is mf, velocity is 80, yet I can select a note in the same measure but a different staff (unpitched percussion, ride cymbal) with the same dynamic symbol (mf), In the Inspector Window, Note category, the velocity is 0. Why the difference?
Comments
'Offset: Make the value shown in "Velocity" relative to the default of 80'
https://musescore.org/en/handbook-basics/inspector-and-object-propertie…
The norm is to see offset = 0, meaning the velocity of the note is whatever the most recent dynamic marking says it should be. If you see some value other than 0 for offset, that means the note will be played that much louder or softer than whatever the dynamic says it should be. If instead of "offset" it says "user", that means the dynamic marking will be completely ignored, and the value you see for velocity will be used instead.
The velocity value you see in the Inspector for dynamics affects the playback of all subsequent notes up to the next dynamic. The value you see for notes affects only that note; it allows you to temporarily override or adjust the velocity set by the last dynamic.
The note's playback velocity is calculated differently depending on the note's velocity type setting:
The defaults are velocity type = "offset" and note velocity = 0, so by default the playback velocity is the velocity of the last dynamic.