This answer is not specific to your model but... most Cadillac horns are inside the front fenders just behind the headlights. There are likely four (yes 4) of them, two to a side, and they are all different. They play C F A and D notes. They may be hidden by other stuff such as the windshield washer bottle.
In a 2000 Cadillac Seville, the horn is typically located behind the front grille, near the front bumper. It is mounted on the driver's side of the vehicle. Accessing it may require removing the grille or other components for maintenance or replacement.
On a 1988 Cadillac Seville, the horn is typically located behind the front grille, near the radiator. It is mounted on the driver's side, often attached to the frame or other components in the engine compartment. To access it, you may need to remove the grille or other surrounding parts.
in the trunk on the driver side
On a 1993 Cadillac Seville, the horn is typically located in the front section of the vehicle, near the radiator support or behind the front grille. It may be mounted on the driver's side, attached to the frame or body of the car. To access it, you may need to remove the grille or other components depending on the specific configuration. Always consult the vehicle's service manual for detailed instructions.
on the middle of the steering wheel
it in the fuse box
On the crossbars of the steering wheel.
In the trunk, remove the back panel by unscrewing the four plastic knobs on the roof of the trunk, there is the entire fuse box for the vehicle
in gloves box
It is located in one of the fuse panels under the rear seat.
The horn is located behind the driver's side headlight. It's attached by a screw and a wire and should be the only thing there.
In a 1998 Cadillac Eldorado, the horn relay is located in the underhood fuse and relay box. This box is situated near the front of the engine compartment, typically on the driver's side. You can identify the horn relay by referring to the diagram on the cover of the fuse box for correct positioning and labeling.