We've been looking at our test piece for Harrogate and I've spotted a curiously ambiguous marking. If you want to flatten or sharpen one of the notes of a trill, where should the accidental go? e.g. in this particular case we are in Eb (Bb pitch), trilling on an F. Most people would instinctively trill F-G, however, there is a natural above the trill line. This would indicate that the upper note should be naturaled- at least in my limited understanding - but as the G is natural, logic would indicate that the natural is meant to mean F-E natural (a downwards trill). But, in that case, shouldn't the natural sign go below the trill line?