Fingering is the choice of which fingers and hand positions to use when playing a musical instrument. For example, when playing the piano, chords or melodies can often be played with a variety of different assignments of fingers to played keys. Fingering, in this context, is the choice of which finger to use for which key, for each note. Fingering typically changes throughout a piece; the challenge of choosing good fingering for a piece is to make the hand movements as comfortable as possible without changing hand position too often. A fingering can be the result of the working process of the composer, who puts it into his manuscript, an editor, who adds it into the printed score, or the performer, who puts his own fingering in the score or in his performance.
Fingering also applies to other instruments, such as woodwind instruments and stringed instruments. Depending on the instrument, not all the fingers may be used. For example, saxophonists do not use the right thumb and string instruments (usually) only use the fingers.
On string instruments fingers are numbered from 1 to 4 where the thumb isn't counted because it doesn't play on a string, and a 0 indicates an open string. In those cases on string instruments where the thumb is used (such as high notes on a cello), it is represented by symbol the shape of an 0 with a vertical stem below (somewhat similar to Ǫ, for instance).
The classical guitar also has a fingering notation system for the plucking hand, known as pima (or less commonly pimac), where p=pulgar (thumb), i=indio (index finger), m=medio (middle finger), a=anular (ring finger) and, very rarely, c=chiquita (little finger). It is usually only notated in scores where a passage is particularly difficult, or requires specific fingering for the plucking hand. Otherwise, plucking-hand fingering is generally left at the discretion of the guitarist.
It is mentioned by Carl Philipp Emanuel Bach (son of Johann Sebastian Bach ) in his book "Versuch über die wahre Art, das Clavier zu spielen" ("trying to write about the true way of playing the piano") he dedicated several paragraphs to this topic, see the German original: "Von der Fingersetzung"
The british pianist Tobias Matthay wrote a small book "Principles of Fingering".
The german pianist Uli Molsen wrote a "Fingersatz-Kurs". The german pianist Wolfgang Ellenberger published an eBook about a systematical nomenclature of piano fingering including a "fingering edition" with different piano pieces.