Development of free-bass keyboard with system of Kravtsov allows to solve the basic problem of repertoire for accordion, and to inculcate the accordion with the same systems of keyboard mechanisms both in the left and right hands. From the point of view of the study of musical instruments, performance, and pedagogy, accordionists received a long-awaited model of the instrument, which is most useful for those playing on organ-piano keyboard. They do not need to master chromatic button systems, which without a doubt slow the progress of the art of accordion playing. Byelorussian manufacturer Zonta (primary - Slava) has already started the production of those keyboards. Suggested free-bass keyboard is based on the mirror imaging of the right keyboard. Why it is done like that, and not like it is in the bayan? A study of this question showed, that processes of movement in playing are acquired fester and more suited for the physiology of people, if they are based up on the mirror countermovement. It is easy to see in the manual technique of conductors. Everybody who held the conductor’s baton, knows how easy it is to conduct with both hands in a countermovement. But, the real conducting does not include such a pleasant physiological movement, as each hand in conducting has its own function and artistic task, and they should not be doubling each other. And it takes a lot of effort to overcome the nature of movement.
Stepwise placement of three rows of keys, furthest away from the bellows, will allow the full functionality of use of the left thumb. 
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