There is a [great answer here](https://music.stackexchange.com/questions/36411/how-can-a-non-musician-recognize-anacrusis) about *recognizing* anacruses, but my question is about how to *perform* them.

The [Wikipedia page](https://en.wikipedia.org/wiki/Anacrusis) has a quote on this:

> 
> An anacrusis may also be evoked solely metrical (non-rhythmical ), i.
>  e. tonal, that is, without the downbeat perception enforced by a
>  relative long value.
> 
> 
> 

I’m not sure what exactly that means, but I think it’s saying that the anacrusis is usually sounded/heard as an “upbeat”, contrasting with the emphasis on the following downbeat, while at other times it can seem to (melodically/harmonically/smoothly/naturally) flow right into the first downbeat and where there is no clear perception of a difference in emphasis. 

My main question is, in regards to piano performance, should one always emphasize the first downbeat more, or at least slightly de-emphasize the anacrusis relative to the first downbeat? I have two particular examples from classical music in mind:
[![enter image description here](https://i.stack.imgur.com/YQpGv.png)](https://i.stack.imgur.com/YQpGv.png)
(Excerpt from Chopin’s Nocturne in E-flat Major, Op. 9/2)
[![enter image description here](https://i.stack.imgur.com/bTH05.png)](https://i.stack.imgur.com/bTH05.png)
(Excerpt from Beethoven’s Sonata No. 1, Op. 2/1)

In the Chopin Nocturne, it is pretty intuitive to the ear that the anacrusis should be played as how I suppose they usually are -- de-stressed/de-emphasized relative to the first downbeat -- and in the case of this popular piece, I basically almost always hear it as such. It is like “taking a breath” on the anacrusis (Bb) and then “breathing out” on the first downbeat (G). However, in the opening five notes of the Beethoven Sonata, this notion of breath certainly doesn’t seem to fit -- not least because it is fast-paced, yes, but also it is a “[Mannheim Rocket](https://en.wikipedia.org/wiki/Mannheim_school)” with strictly ascending notes of the same value. To my memory, I have heard András Schiff, a renowned pianist, comment that the anacrusis should be played like an upbeat (even if just/albeit subtly). I have listened to some recordings by other famous pianists: Barenboim, for example, doesn’t seem to subtly play it as an upbeat (or maybe he does, I can’t hear that precisely), while Schnabel does.

Is this a matter of interpretation in more equivocal cases like the Beethoven Sonata? Is the existence of an anacrusis in cases like the Beethoven Sonata more because of theory or such, or simply just a matter of composition and the composer -- in this case I suppose there are five notes because, well, Beethoven wanted five ascending quarter notes starting on the C, but it’s in 4/4 so there kinda had to be an anacrusis.

Sorry if this question comes off as lengthy and pedantic -- I kinda simply enjoy seeing what other musicians in this knowledgeable community might have to say about more specific stuff like this. I also just really enjoy many of these classical piano pieces and would like to know how to best perform them, whatever that may mean.