Articulation Tip: don't forget the appoggiatura!

I recorded the air "C'est bien a tort" by Bacilly as demonstration material for a learner of mine. In the recording, I caught myself in a passage which I think would be interesting to talk about. And in case you're wondering, the upper line is in soprano clef, which is like reading G clef a third lower.

So where the red asterisk is, we have a trill on a C (also marked with x), and the note before the trill is a D. We have here a situation where the note before a trill is the same as the appoggiatura of the trill. This often creates a bit of confusion and we easily lose clarity between the notes (in this case two D's). The goal is to still have a distinction between these notes, however subtle that distinction should be. The trill falls on the "ssens" of the word "ressens" and we'd want to reflect that fine nuance of the "ss".

We can achieve this by gently ending the sound of the first D with the tongue, and then making sure to start the trill with the appoggiatura. Bring the tongue back up to the roof of the mouth, right about behind the front teeth. This will make the tongue end the first D and also be ready to start the appoggiatura D. You should feel a slight resistance on the tip of the tongue right before you start the next note. This refined coordination also needs a fraction of time to make sure the D appoggiatura really sounds and doesn't get swallowed, otherwise the trill would then become like a mordent or something. That's what happened in my initial recording, and when you're familiar with the style and expression, it sounds a bit out of place. 

I want to point out that this is not just a dogmatic following of the principle that we should start trills on the upper note, but there are musical reasons for doing so. With a quick and light appoggiatura, the trill here should sound like a slight tremble in the voice, or simply a flutter in the air. The two D's also make the line very smooth, which makes sense here for the expression. In addition, immediately retract the breath after the appoggiatura to further enhance that wistful affect.
Compare if you'd play something like C-D-C on the C as the ornament (so omitting the appoggiatura) - I find it takes away from the "leaning" effect of the appoggiatura, which then also reduces the tender, yearnful expression here. 

Don't forget that, beyond vocal airs, we can make the same observations in numerous instrumental music. In fact, French flutists were first playing these airs de cour before specific flute music came into existence, as well as the common ideal for any instrumentalist was the human voice. So certainly in lyrical pieces, their playing would reflect a strong vocal tradition. The expression of ornamentation is also one of the hallmarks of baroque music. The very fine details convey expression and thus require a specific way of execution. There are usually a good number of clues in the music to help us decide on our interpretation, and what we know as "rules" have certainly musical reasons, not just theoretical ones.

Below is my demonstration video: