Harmonica key of C. Tremolo tuned harmonicas are mainly used in traditional folk music. Blow and draw notes are situated in adjacent holes and the individual channel openings are horizontally divided into two, whereby the upper and lower half each contain one blow or draw note which sound simultaneously, in contrast to the single note arrangement used in Richter harmonicas. These notes are tuned to the same pitch but a few cents apart, so that they create a tremolo effect when played together. The resulting sound is characterized by a light, pulsating quality which is pleasing to the ear.