Thank you all for your replies, and for your encouraging comments.
In reflecting on what you have said above, what's coming up for me is a sense of "travelling". That music isn't just a series of one-off notes, but a journey through notes (and rests). I wonder if being musical is about how
one travels through the notes? And what that journey image conjours up. Because I am mostly a visual person I find that different music creates different pictures in my mind - it's as though the music I am hearing is the soundtrack to the film I am running in my head. Being able to convey that film to others through my singing is another matter though!
And as I'm saying this I'm also thinking that it's important to have a sense of the overall shape of the piece, not just the moment by moment details. So that you have an idea of where the journey will eventually end up.
Thank you everyone. Your comments have got me thinking about this whole subject in a different way.
PS And what a gorgeous sunny day it is too.