The steps to change the music on the wall clock are as follows:

1. Remove the wall clock: First remove the wall clock from the wall or bracket to ensure that you can easily access the internal parts of the wall clock .

2. Open the wall clock: Depending on the design of the wall clock, find a way to open the wall clock, which may be by removing the back cover, side panel or other methods. Note that this step requires caution to ensure that the wall clock is not damaged.

3. Locate the music box: Find the location of the music box inside the opened wall clock. The music box is usually located at the base of the wall clock, or placed in a dedicated compartment.

4. Remove the original music box: Carefully remove the original music box. This usually requires removing or unfastening the screws or clips that hold it in place.

5. Purchase and install a new music box: Purchase a music box that suits your preference at a nearby watch/clock store or online. Make sure the music box and wall clock you choose match the size and design.

6. Connect the new music box: Connect the new music box to the corresponding position on the wall clock. This may require some simple adjustments and fixings between the music box and wall clock.

7. Close the wall clock: After confirming that the music box is firmly installed, cover the wall clock and secure it.

8. Hang the wall clock: Hang the wall clock with the new music box installed on the wall or bracket.