Although not normally used, each player should have an accordion in key C. Most of the instruction manuals and music are written for a C accordion, making it a pretty indispensable tool. Although rarely used in reality, it is still an important exercise tool.
Straight and cross Harp
There are two common ways to play the accordion, each of which changes the key used in the accordion. Straight harp has the root note like the blue in the fourth hole. This root note is the same as the key. Harmonic notes form the main scale of the root note.
Cross harp is common in blues and rock music. It uses the drawing note in the other hole as the root note. This changes an accordion to the Mixolydian mode – the root note is the fifth key in the accordion to be used. For example, a song in D-played cross harp should be played with a G-accordion. Players must adjust the key development they receive accordingly.
A solo accordion player can play anything they want with a C accordion, as long as they correctly transcribe the songs. Players with a band must get accordions to match the key to the songs being played, which varies depending on the band and style. Blues and rock players should definitely get accordions in A, D and G. When playing in the cross strokes, the A accordion is used in the E. key. The D-accordion is used for the key to the A. D-accordion forms D, which is less common in rock and blues. The third position (fourth perforated note as the root) is useful for some songs with a lesser feel. D harmonica is used over E minor songs. The G-accordion goes over a minor, which will be the most common use for it. The A-accordion forms B-minor, which will not be as common.
In other band situations, it’s just a matter of finding which keys the band benefits from. It is much easier for an accordion player to change accordions than it is for a vocalist to change his range. There are rock and blues bands that do not have any songs in A or E, which means that conventional wisdom will not apply. Most harmonics are diatonic instruments, designed to play a key. While it is possible to force the accordion to play outside this key – using bends – it is easier to use an accordion for the appropriate key. Most players will end up having a few different key harmonics, but some will be more useful than others.