First of all, you have to bake your cake in the baking pan or a guitar shaped baking pan. Keep observing the cake when put it in the oven so that it may not get over heated.
Then, take the cake out of the oven and keep it aside to cool down. After that, you have to add the icing. You can add icing with the icing bag. It will be better for you to take a printed picture of a guitar with the dimensions of the cake size. In this way, you will be able to cut the cake in a more profound manner without making any kind of mistake. On the other hand, if you baked the cake in a guitar shaped baking pan, you don’t require any picture of guitar.
Now, you have to add colours to the cake so as to make it look like a guitar. Use white icing to paint the middle plate of the guitar shaped cake. Furthermore, you can use black icing to paint the neck of your guitar. In addition, you can use the yellow icing tip for the guitar neck.
Use red icing in order to cover the remaining body of your guitar. Besides, use black icing to paint the strings and frets of the guitar.
After painting the guitar with icing, add any topping if you want and serve.