Auxiliary tone of trill

[arvidb]

I'm a bit uncertain about how to find the upper/auxiliary tone in a trill. I've read it's supposed to be the "next tone in the given scale". But what happens when the base tone has an accidental?

To give specific examples, look at bar 30 and 32 in movement 3, Presto agitato, of Beethoven's Op 27 No 2 (mhmm, the "Moonlight" sonata).

Bar 30: the base tone is A#, auxiliary tone B? (And the auxiliary would have been B even if the A had not been sharp, since B is the next tone in the movement's key?)

Bar 32: the base tone is G (F double-sharp), auxiliary tone G#?

Is this correct?

Thanks, Arvid

[pianistimo]

there's an article here about how strings and voice are related to the interpretation of trills:

www.standingstones.com/stringvib.html

and about trills at
www.dolmetsch.com/musictheory23.htm  scroll down to trills.

i tend to use the notes that are indicated (if they have a flat or sharp sign above the trill - then you know that it's probably not a diatonic note).  i think beethoven tends to use diatonic notes for upper auxillary, doesn't he?  he kind of assures this by using non-diatonic notes for lower auxillary, sometimes, right?

[arvidb]

Interesting reading about trills in those links, but I didn't manage to really find an answer for my question, though.

When you say you use the notes "that are indicated", what do you mean? I know an accidental symbol above the "tr" sign affect the auxiliary - but how do I find the "unaffected" auxiliary? Is it always the next diatonic (i.e. from the scale) note?

And how would using a non-diatonic note for lower auxiliary assure a diatonic note for upper auxiliary? Oh, and when you say lower auxiliary, are you talking about the written note or the note below it?

I'm seriously confused here...

Arvid

[faulty_damper]

The next tone is the next note/letter.  This is true regardless of any accidental.

So if it is an A# (or natural or flat), the auxilary note must be B since it is the next note/letter.

G is NOT the same as F double sharp. F## is F##.  In this instance, it is a leading tone to G# (because G# is in the key signature).  You are correct that the auxilary note is G#.

[faustsaccomplice]

Hey Arvid

It will always be the next tone up in the scale, unless the composer writes an accidental above the trill sign.  In the example you've given in the Moonlight Sonata, the trill on f-double-sharp would have an auxiliary note of g-sharp, because gs are sharp in this piece.   

When a "non-diatonic" note has a trill on it, it will still be the next note above in whatever key you're in.  So, hypothetically speaking (not that this would be likely to happen), if we were in the key of G major, and there were a trill on e-double-sharp, and no accidental above the trill, it would just be a repeated note.

The good news, Arvid, is that it's more simple that you were thinking.  If this doesn't answer your question, let me know and I'll try to be of help. 

[faustsaccomplice]

The next tone is the next note/letter.  This is true regardless of any accidental.

So if it is an A# (or natural or flat), the auxilary note must be B since it is the next note/letter.

G is NOT the same as F double sharp. F## is F##.  In this instance, it is a leading tone to G# (because G# is in the key signature).  You are correct that the auxilary note is G#.

you posted this while i was typing mine...i think you've answered it too.

[arvidb]

Thank you both, faulty_damper and faustsaccomplice, for great answers! I believe I got it now:

Look at the *written* note, disregarding any accidentals, take the next one, and if this happens to be flat or sharp in the current key signature, use that accidental (unless there's an accidental written above the trill sign, in which case that accidental takes precedence).

I had it wrong in two ways when I wrote my question, but still managed to wind up on the correct note!

Arvid