‘idio-‘‘
combining form personal, own
‘dextrous’
adjective showing or having skill, especially with the hands
‘Idiodextrous’ is an adjective created to describe the ‘handedness approach’ of people who play string instruments ‘back-to-front’ or ‘upside-down’, playing ‘left-handed’ on a conventionally ‘right-handed’ instrument (or vice versa) without restringing it, such that the order of the strings in relation to the body is the inverse of the traditional one.
The noun form of the word is ‘idiodexterity’, which refers to the phenomenon in general.
In the original research, it was only used to refer to playing ‘left-handed’ on a ‘right-handed’ double bass, but it can be applied to any string instrument as long as:
1) the handedness approach is different to the conventional one; and
2) adopting this approach changes the order of the strings in relation to the performer’s body.
On this website, you will find a database of idiodextrous musicians from all around the world, playing all kinds of string instruments in all kinds of musical contexts.
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idiodextrous 
I’m a lefty double bassist but sometimes when touring I won’t bring my bass but use a right handed one that’s in the new town so have to play idiodextrously. The clarinet player of a band once wanted to see me do this before one tour so I borrowed one from a school I teach at to show him. As a lefty, I’ve had to play righty guitars and basses for so long, I don’t think about the change too much though of course can’t play as involved lines (or chords) as I can on a proper lefty.
David
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