About your horn:
If you need to rev up your engine to get your horn to “oogaaah” correctly it may have shorted windings and need to be rewound.
If you have problems adjusting your horn it may need to be rewound.
With proper lubrication and normal battery voltage you should be able to adjust your horn for that special model A sound, if not it may need rewinding.
This video explains how to easily remove the old wire and rewind the Model A horn new modern enamel-coated wire.