How to play first trill in Mozart's sonata K576?

Question

How should I play the first trill in Mozart's Piano Sonata No.18 in D major, K.576 ?

I am currently playing it like this:

(or I may play it as a a triplet in thirty-second notes followed by the the two thirty-second notes as explicitly given for the termination of the trill. The tempo is quite fast so it is difficult to note a difference between this and the first case of a quintuplet in thirty-second notes)

However, my piano teacher noted that the trill should start on the auxiliary note (the note above the one indicated). I also found a similar statement in Wikipedia:

In the baroque period, [...] trills in this era are executed beginning on the auxiliary note, before the written note [...] Continuing through the time of Mozart, the default expectations for the interpretation of trills continued to be similar to those of the baroque. In music after the time of Mozart, the trill usually begins on the principal note.

Answer 1

Evidence

Your teacher's advice is consistent with the evidence.

The most natural source to use is Leopold Mozart. You will find that his recommendation is that all such short trills should begin with an appoggiatura.

From chapter ten which discusses trills:

Mit einem schnellen Vorschläge und Nachschläge spielt man alle kurze Triller.

That is, in this context, all short trills are played with appoggiatura and turn.

C. P. E. Bach is exhaustive and of great historic importance but should perhaps not take precedence over Mozart's father in this case. At any rate, he disparages beginning on the principal note.

Whether you play the flute or not, it is also very beneficial to read the essay by Quantz.

In your example, choosing the upper note start, you would play six notes or four, depending on the tempo. When the tempo chosen is most rapid, I am sure I have heard celebrated performers use only four. For example, I seem to remember Barenboim did this, simply adding an appoggiatura to the notated figure.

Added 8th May

There has been discussion in comments concerning the historical basis to beginning with the principal note. The question is: what evidence of the practice do we have from Mozart's lifetime applicable to trills like those in the OP?

A colleague has alerted me to the book Perspectives on Mozart Performance (1991) which contains an article by Badura-Skoda on Mozart's trills. This article discusses internal evidence in Mozart's works relating to the choice of trill execution: presence or absence of turn, presence or absence of appoggiatura, and so on.

I will not have an opportunity to consult this work at the library until next week. In the meantime, if any reader has it, please leave a comment.

Guidance

A comment about Wiener Urtext edition raised the question of how we might decide for ourselves whether to start on the upper or principal note. Frederick Neumann in his Ornamentation and Improvisation in Mozart (1986) proposes this algorithm:

1) a trill starting with the upper note on the beat has the effect of a short appoggiatura; 2) a trill starting with a lengthened upper note has the effect of a long appoggiatura; 3) a trill starting with the upper note before the beat has the effect of a grace note. We find guidance by leaving out the trill and judging whether one of these ornaments would be a desirable addition to the bare melody; if so, the corresponding trill type is likely to be the proper or at least an acceptable choice. Where none of these ornaments seems to fit, the main-note trill is indicated. Where no clear-cut choice between one or more of the alternatives emerges, more than one trill design will be fitting.

This algorithm still leaves room for difference of opinion in whether the substituted ornament is acceptable.

Answer 2

Whatever the rules might be, surely context has to be an important consideration (after all, rules are made to be broken!). In this passage, starting on the upper note (D in the first trill) sounds fussy to me, and also less effective as it ends up resolving on the same D. Playing it as a quintuplet starting on the principle note sounds and feels more natural. That's my suggestion - you must decide for yourself what feels and sounds best. According to the KV number, it is late Mozart, so the tradition of trilling from the upper note would be becoming obsolete somewhere near that time anyway.