You can tell when the music is going to turn right because it slows down...When I was learning to drive, my father gave me the advice that you shouldn’t rely on other cars’ indicators to work out what they were going to do, but instead take note of their road position and speed. It’s quite possible for someone to have failed to cancel their indicator, or for them to think they are using it, but the bulb has gone, and if you rely on that misleading information to make decisions, you could cause an accident. So, he taught me, make your judgements about what other drivers are likely to do by seeing how they’re driving, and look at the indicators for confirmation. Likewise, drive in such a way that other drivers can tell what you’re going to do.
Much the same principle, historically, applies to dynamic markings in music. Musical shape (texture, harmony, voicing, contour) tells you a lot about how you should perform the music if you attend to it. Rose Rosengard Subotnik wrote about the proliferation of sforzandi in Beethoven’s music as indicating a ‘loss of semiotic certainty’, reflecting a need to add extra, paramusical information about the ‘how’ through a fear that it would not otherwise be played as it should be. Those 19th- and 20th-century editors who littered older music with extra layers of instructions likewise seem to evince a mistrust of performers’ judgement.