There are three commonly encountered tunings or note layouts used for tremolo harmonicas. The older layout is very similar to that used in the standard diatonic harmonica and also found in diatonic accordions and concertinas. This tuning has the major diatonic scale in the middle and top octaves of the harmonica with two chords in the lowest octave: the tonic in the blow and the dominant or fifth chord in the draw. This is very effective for chordal playing behind relatively simple folk melodies in either the tonic or the fifth of the key of the harmonica. In Asia, the fourths and the sixths are added back in, in order to play the melody; however, it is still unlike the scale tuning mentioned below, since the octaves are not repeated throughout the layout.