Horn issue...it should be two-tone, right?

[norfolkcali]

I think I might have a horn issue on my 2010 Cali SE, I think it's gone form a meaty two-tone to a weedy single tone parp. And I always thought that the horn could be activated with the ignition is off, or have I got that wrong? I've checked all the fuses in the dashboard and they are all intact.
Is this a garage job or something for an auto electrician? Thanks in advance...

 

[CaliforniaDAN]

Have you checked the connections on the horn itself in the engine compartment?
They could be loose or even debris in the horn as well