How do you know whether to trill up or down?

[ranjit]

Is there some kind of rule?

[brogers70]

Is there some kind of rule?

I think you mean whether you start the trill on the principal note or the note above it. I assume by "trill up" you men start on the principal note and by "trill down" you mean start on the note above the principal note.

There are lots of rules that varied over music history. The shortest rule would be that in the Baroque and early Classical period trills start on the upper note (above the principal note = "trill down", I guess). And that later, there is more tendency to start on the principal note and "trill up."

In part that is because in the earlier music the trill often arose as a sort of suspension, briefly dissonant with the harmony under it, and that character is emphasized by beginning on the upper, dissonant note. There are lot of arguments about the details, like what happens when you descend stepwise to the trilled note - do you then, trill from above, as the simple rule says, which involves repeating the note immediately above the principal note, or tie the preceding note to the first note of a trill from above, or do you trill from below. In spite of JS Bach's nice table of ornaments, there's not even consensus as to what should be done in all possible cases even in Baroque music.

https://www.pennuto.com/music/jsb_ornm.htm

[ranjit]

That's a less well-defined answer than I had hoped! Thanks for all of the relevant info.

I think that Chopin tends to trill "up" a lot. I used to always start on the note rather than the adjacent one until I realized it was possibly wrong.

[lelle]

My rule of thumb is generally that up until the romantic era including Chopin the trill starts on the upper note if the preceding note is on the same pitch or comes from below, unless taste dictates otherwise (a violent Beethoven trill à la hammerklavier with a sforzando on it should probably start on the note, whereas a gentle trill in an early sonata starts on the upper note). If the preceding note is a 2nd above (i.e. the same as the upper note on the trill) one can consider if it is better that the trill starts on the note.

In later romantic music one can assume the trill starts on the note unless otherwise indicated.

You'll often have to figure it out based on the context, your knowledge of the style and music theory, and intuition built up over time.

[nw746]

I was taught that trills generally start on the auxiliary note prior to Haydn & Mozart, and on the principal note from Haydn & Mozart onwards.

Mozart, whose notation was always very clear, always indicated specially when he wanted a trill to start on the auxiliary note. For example:

The appoggiatura in front of the third trill indicates it should begin on the auxiliary note. The first two trills, since they have no appoggiaturas, obviously should then begin on the principal note (as should any other "un-appoggiaturaed" trills in Mozart, or Haydn or Beethoven etc).

Chopin followed a similar rule to Mozart except that he occasionally and exceptionally also indicated appoggiaturas on the principal note (although first editions have these as accacciaturas [i.e. before the beat rather than on the beat], which makes a bit more sense).

[dw4rn]

Mozart, whose notation was always very clear, always indicated specially when he wanted a trill to start on the auxiliary note. For example:

I don't claim to be an expert, but even if this view is correct, it is not generally subscribed to. I am sure we could easily find hundreds of Mozart trills where 999 of 1000 performers will start on the upper note even if Mozart wrote no appoggiatura.

Appoggiaturas may have been used in the way you're describing, but obviously they also have other functions unrelated to trilling, which seems to me to make them unreliable as evidence in this particular case. 

[nw746]

I don't claim to be an expert, but even if this view is correct, it is not generally subscribed to. I am sure we could easily find hundreds of Mozart trills where 999 of 1000 performers will start on the upper note even if Mozart wrote no appoggiatura.

I don't deny that most performers are wrong.

[dw4rn]

Ok, so what are your sources, except that

I was taught that

[lelle]

I was taught that trills generally start on the auxiliary note prior to Haydn & Mozart, and on the principal note from Haydn & Mozart onwards.

Mozart, whose notation was always very clear, always indicated specially when he wanted a trill to start on the auxiliary note. For example:

The appoggiatura in front of the third trill indicates it should begin on the auxiliary note. The first two trills, since they have no appoggiaturas, obviously should then begin on the principal note (as should any other "un-appoggiaturaed" trills in Mozart, or Haydn or Beethoven etc).

Well not exactly correct. Notice how the appogiatura is a quarter note? It means you hold the first (upper) note for a longer time before you start trilling. It'll be realized something like an eight note in practise, and then the trill starts. But it does not mean that the other trills start on the note, just that the first (upper) note is not held for a longer time in these cases.