A certain % of people can curl their tongues. If you can do that it makes harp playing easy as you can block all the holes you don't want to sound. Straight harp, playing the same key harp as the song, is also called 1st position. Second position is cross-harp, the harp corresponds to the IV cord. (play E and suck on an A harp). There is also a 3rd position but involves never playing some of the notes. What this means is you can play in three different keys using just one harp.