Libba Cotten and Jimi Hedrix both played right handed guitars left handed. This may be the only time both are mentioned in the same sentence.

Although most people are more dextrous with their right hand (OK, OK!) the right side of the brain controls the left hand and vice versa. The right brain mainly deals with spatial information and the left brain with sequential information such as language. I've thought for some time this might explain why the left hand is used for harmony work, eg chord shapes on guitar, piano etc, and the right hand picks out the sequential melody. It doesn't explain instruments like fiddle, however, or chromatic banjo styles.

Undergraduate psychology degrees don't go into psychology of music, so I never got to pursue this. Left/right handedness is a huge subject and this is not even a dabble in it.

dj