A little help

[stevel]

Also, that would mean everything in my third movement (where the tune is put in) is under copyright to me (if it ever gets to that), except for that tune itself. If so, that's fine.

Your setting of it is copyrighted. But yes, the original tune itself remains public domain - it's usually for this reason when using such a tune (when someone's worried about it) the tune is set or modified in such a way as to make that setting unique.

Also, about my avatar, I didn't think about someone copying it. I might as well change it when I can be bothered.

I wouldn't worry about it too much - unless you are worried about it. It's not really enough to steal your music from - all you'd really be protecting is the effort you went through to make the image in this case.

Best,
Steve