Hi all,
I found this at Dolmetsch music theory,
"In the seventeenth century the word 'grace' was applied to a number of 'ornaments' including the appoggiatura (from an Italian word meaning 'to lean') and the acciaccatura (from an Italian verb acciaccare meaning 'to crush'). The acciaccatura is very short (literally 'crushed'), is played on the beat together with, or imperceptably before, the principal note before being released. It is generally, although not always, written as a small quaver (eighth note) with a stroke through its stem and lies in front of the principal note. The appoggiatura is usually written without a stroke through the note's stem. In both cases, the notation of the grace note is symbolic - the grace note (with or without a stroke through its stem) is not included in the time value count for the bar.
Apart from the requirement to play them as quickly as possible, there was no 'hard and fast' rule as to whether these 'passing' grace note sequences were to be played on or before the beat."
The American Heritage dictionary has, "An ornament note that is one half step or one whole step higher or lower than a principal note and is sounded at the same time as the principal note, adding dissonance to a harmony."
So, no wonder I'm confused. Inconsistent notation and variations in performance practice are to blame.
That's all for now, Joe.