My own Silver Harp was made by a bulletin board, some copper pipes, special wire, aluminum foil and tacks. I used the foil to make the sound vibrate more than nothing. How I made the pitches different is that I pluck the strings and if I want to make the sound higher I would pluck the strings that were shorter. To make the volume louder I would pluck the strings harder than normally. If I wanted to make the sound softer I would pluck the strings softer.
I have learned a lot from making this instrument and about volume and pitch.