Once you start playing with other musicians, you will need to get some extra harps in different keys, or else you will be very limited in what you can play along with. The more harps you have, the more keys you can play in. Each key will have a slightly different character. Low notes sound great on low tuned harps such as a G harp, while bends can sound more intense on a higher harp such as a D harp. The most commonly used keys are A, D, G, C, F and B flat. There are harps tuned in all twelve keys, but these ones will get you through most musical situations.