Harp
The folk harp is the older kind of harp, the oldest dating back to 3000 BC in Ancient Egypt. In these harps, each string can only make one note at a time. They are usually tuned so that playing each string in order sounds like playing all the white notes on a piano in order. This is called a diatonic scale. In some places, they are tuned so that playing each string in order sounds like playing all the black notes on a piano in order. This is called a pentatonic scale.