TextSpanner Y-offset

[Andrew Bernard]

According to the internals reference manual, the Y-offset of a text spanner is the distance from its Y parent. Apologies if this is a foolish question, but what is the Y parent of a text spanner?

I have noticed in my scores that sometimes setting the Y-offset has no effect until some sort of threshold number is reached, and even sometimes there is no effect at all and the spanner wont move. What is this parameter relative to?

Andrew