I know this is a question that’s been asked before, but I haven’t found an answer that suits my needs.
Consider the following example [edit: new excerpt, to include all swells and to remove other staves as requested]:
As you can see, there are several swells in this string passage (the rest of the string section uses identical dynamics). This is following an (unshown) intro in pp, hence why I want the first swell to be louder (p). Each swell is intended to sound louder than the last, with the final reaching f (but no higher, as there are louder climaxes later).
What should I write in the space of ? to indicate a dynamic between mp and mf? Is there something that means “louder than mp but not quite mf”? Until recently I used m, but many say that’s too ambiguous.
Edit: I’ve received some informative answers and comments and I appreciate them all, and I intend to implement the things I’ve learned in my scores. But I don’t think I’ve yet received an answer to the specific question of whether a middle-ground exists between mp and mf and how to notate it, in the event where this were necessary (assuming you couldn’t upshift or downshift other dynamics for whatever reason).
For instance, would having a passage play mp and then adding a cresc. hairpin (that doesn’t end with a written mf) work? (This assumes both mp and mf are used further along, and that you want gradual “steps” in volume.)