NOTATIO

In a discussion in another place, it was suggested that dim. can mean a slowing down of tempo as well as volume. Schubert and Chopin were cited. However, most people were unaware of this usage.

I'd never come across this usage either (19th-century piano not my 'forte'), so how best should such possibly misunderstood usage be conveyed to the reader?

Similarly, Pergolesi alternates between 'dolce' and 'forte' instructions, which suggests that the former is more of a dynamic than a mode of expression. (Piano is never used.)

So: where does the balance lie between faithful transcription and use of terms with modern accepted definitions? (On the assumption that the readership may not all be musicologists. ) Should the particular meaning be laid out in explanatory notes, or should they be changed, to avoid ambiguity with their modern meaning?

FWIW (maybe not much) I think I'd probably prefer to see the original directions, if not completely incomprehensible for someone used to modern notation, plus a clear and simple note of explanation.

I agree with David.

In earlier music, performance directions are often in the nature of hints than the more exact markings were are now accustomed to and for this reason any particular marking (and this includes the symbolized ornaments) can mean different things depending on context. For this reason, explanatory notes are now often necessary. But in every case, I would want to see the original indication to be able to decide for myself.