An important part of interpreting music is figuring out how to use dynamic markings. They aren’t as simple as just playing louder or softer.
It helps a lot to understand the difference between what I call local dynamics and big-picture dynamics. Unfortunately, they are marked in sheet music using the same symbols, so it’s not always immediately obvious which they are. When you study a new repertoire piece, ask yourself why the composer or editor has provided each dynamic marking:
Is it there to call attention to a major event in the music, like a new theme, a return to an old theme, or some other kind of climactic moment? If so, it’s a big-picture dynamic. In many cases there is some other evidence that this is an important moment: a double-bar, a fermata, a key or tempo change, an entrance after some rests, etc. (If you have studied musical form, you probably have some more ideas of what to look for.)
Or, is the dynamic marking there just to provide some shape and direction to a phrase? There’s no major musical event, just a hint about the momentary musical gesture. If so, it’s a local dynamic.
When you think in terms of local vs. big-picture dynamics, it’s clear that not all fortes or mezzo-pianos or crescendos are equal. If the composer uses dynamics to contrast two themes or sections, for example with one being soft and the other being loud, that probably calls for a dramatic change. (It may also hint that some other unwritten contrasts are appropriate, like nuances of tempo, articulation, or tone color.) But a one-measure decrescendo from forte to piano in the middle of a theme might be more of a suggestion from the composer about what direction that phrase should take, and should be handled with more subtlety.
Beware of the limitations of dynamic markings in music notation, and of careless editing, and use your best-informed musical judgment to interpret the meanings of those symbols.
