Instructions (Part I): Click here, here and here to access a few different pre-built online instruments that can be easily integrated with the MakeyMakey.
Instructions (Part II): Using the information above, and in the previous activity, build a MakeyMakey controller for one of the instruments above. You can use materials like cardboard from boxes, pencil markings, etc. See the video below for an example. Test and revise your instrument.