Bayan, accordion and harmonica are popular reed musical instruments that have both common features and significant differences. They all belong to the group of harmonicas, in which sound is produced using metal reeds driven by air flow from bellows. However, their design, purpose and sound capabilities differ markedly.

Bayan is a chromatic harmonica with a right button keyboard and a left bass keyboard. It has a full chromatic range, allowing complex classical pieces to be performed. The accordion, unlike the bayan, has a piano keyboard on the right, making it more intuitive for pianists. The harmonica is a diatonic instrument, typically with a limited range and fewer voices, which determines its use in folk music.

In terms of construction, the bayan and accordion have complex sound production mechanisms with the ability to switch registers, allowing timbre changes. The harmonica has no registers, usually having 1 to 3 voices. The number of voices of the bayan can reach up to 10, the accordion up to 5, providing a rich sound palette.

The range of the bayan is the widest — from 4 to 6 octaves, the accordion has about 3-4 octaves, the harmonica — 2-3 octaves. By keyboard type, the bayan uses buttons, the accordion uses piano keys, the harmonica also uses buttons, but arranged differently.

Sound effects and settings on the bayan and accordion include the ability to switch voices and registers, allowing imitation of various musical instruments. The harmonica has no such capabilities, its sound is simpler and not customizable. The classification of all three instruments is generally similar: they all belong to the harmonica family, but the bayan is more often used in academic music, the accordion in pop and folk, the harmonica in traditional folk.

Thus, the choice between bayan, accordion and harmonica depends on the task: for classical music the bayan is better suited, for pop music — the accordion, for folk music — the harmonica. Each instrument has its own unique advantages and disadvantages.