Guidelines vs. Rules

❓So a common question I get is asking about rules in historical performance. What are the rules for playing *fill in the blank*? I try to answer by saying: there are guidelines, and some are even pretty "set", but what's also necessary is to look at the context, listen, and make choices based on this process.

I thought to use a recent question I got as an example. The question concerns whether to place some of the ornaments in Hotteterre's Suite in D major on the beat or not. Let's look at the Sarabande "la "d'Armagnac". The circled ornament is a double port de voix, which occurs throughout the movement. But even if you didn't know anything about this ornament, there are usually other indications in the music which can help us to determine whether to play it on or before the beat. So in a sarabande, it makes sense to play it on the beat because of that characteristic sarabande emphasis on the second beat. Compare playing it both ON and BEFORE the beat, and you'll hear that playing before the beat won't give that clear rhythmic, LIFTING gesture. Also, what speaks for playing on the beat is that the ornament creates a slight dissonance with the C# in the bass, which adds harmonic richness and further enhances that second beat. 

​A tierce de coulée (falling third) occurs, on the other hand, often at the ends of musical gestures, or kind of like "on the way to something". The general affect is also soft, flowing, maybe sighing, and so is usually played before the beat. Hotteterre's Menuet illustrates these concepts perfectly, and especially the string of tierce de coulées in the second line sets up an effective contrast against the rhythmically more obvious (and usual) opening phrase. In this second line, the thirds fall gracefully from the half note, avoiding a strong down beat and thus creating a metric displacement. Together with the bass line, we have for a short while here a very interesting juxtaposition of rhythmic details which makes this Menuet special! If you'd play the tierce de coulées here on the beat, the dance would lose these special qualities, become heavy, and go against the natural musical intentions.

Now in the Prelude of this suite, we have something that sort of looks like it could be a tierce de coulée (see asterisk). What are some other clues in the music that can help us decide whether to play it on or before the beat? In this particular moment of the music, there's harmonic tension happening with that 7th chord underneath, and also since it's a Lentement in 2, placing the ornament on the beat helps contribute to the affect and metric structure. It should sound deliberate, a bit "heavy", and playing before the beat would then reduce the poignancy of the phrase. The same idea goes for the ornament after that.

And see further in the next line, a tierce de coulée is appropriate after the G# as it brings a little closure before the leap up to the A, and it's also metrically the weakest part of the bar and naturally wants to fall from the preceding trill. Thus, better before the beat.

So by looking at the context of the ornament we can also take some clues already about the expression, which would then help us to decide how we want to execute it. There's a musical meaning, rather than simply being a type of ornamentation with automatic "rules" on how it should be played.