Sick Ahh-Ooh-Gah

[29Cabriolet]

The title should suggest where I am going with this post. My horn kind of sounds Ahh-Ooh-Gah, but is barely audible. When on the road and RPMs are up of course it's a bit louder but still quite weak. Would this seem to be a problem with the horn itself or more likely an electrical problem or deficiency? I am still 6V with stock generator, no voltage regulator or other "modernization" add-ons. Suggestions?

Thanks!