Determining dynamics of individual parts in music group

Question

I have been lately wondering how to determine dynamics of individual parts in music group. As we all know sheet music many times doesn't provide all dynamics and phrasing.

It seems obvious to me, that when you have for example two parts that play the same melody in lets say thirds, dynamics must be the same. But what to do with other lines that don't play the main melody? What to do when you have two melodic lines and one or two accompaniments? Should accompaniments strictly follow all dynamics, should they just stay below the melody always at the same dynamic level or follow melodic dynamics just to some extent? What to do for example in baroque music when you have some lines that are not the main melody but also not just some "boring" chord accompaniment?

I hope that my question is not too broad. If it helps, at the moment I'm mostly interested in late baroque music (Vivaldi, Bach).

Thanks in advance!

Answer 1

You determine it using your artistic judgement. Maybe the melody needs to be 'brought out', maybe it will shine through naturally be virtue of being the top line. I'd say the latter was the more likely for a passage in thirds. @Dekkadeci disagrees. That's fine!

If we're talking Baroque keyboard music, it was very likely conceived for organ or harpsicord, where all the notes playd on the same keyboard had equal, fixed volume. (And then Glenn Gould comes along and plays them on piano with lots of 'expression', to the pleasure of some, the dismay of others!)

Answer 2

Most often composers will give the same dynamic for all parts, and allow the performers to decide what's required for good balance. There are of course some composers who dutifully give prominence to certain instruments through dynamics, but other than that it can usually be settled during rehearsal quickly enough.

In fact, Baroque music is often rather lacking in dynamic markings in the original manuscripts. Then the editors take over. Because Baroque music is often so contrapuntal (thinking of JS Bach in particular), you'll find that there's a lot of interest in most of the parts, and this is why it's easiest to leave it to the discretion of the performers.