Guidonian hand
In Medieval music, the Guidonian hand was a mnemonic device used to assist singers in learning to sight-sing. Some form of the device may have been used by Guido of Arezzo, a medieval music theorist who wrote a number of treatises, including one instructing singers in sightreading. The hand occurs in some manuscripts before Guido's time as a tool to find the semitone; it does not have the depicted form until the 12th century. Sigebertus Gemblacensis in 1105–10 did describe Guido using the joints of the hand to aid in teaching his hexachord. The Guidonian hand is closely linked with Guido's new ideas about how to learn music, including the use of hexachords, and the first known Western use of solfege.
Guitar fiddle
From such evidence as we now possess, it would seem that the evolution of the early guitar with a neck from the Greek cithara took place under Greek influence in the Christian East. The various stages of this transition have been definitely established by the remarkable miniatures of the Utrecht Psalter. Two kinds of citharas are shown: the antique rectangular, and the later design with rounded body having at the point where the arms are added indications of the waist or incurvations characteristic of the outline of the Spanish guitar. The first stage in the transition is shown by a cithara or rotta in which arms and transverse bar are replaced by a kind of frame repeating the outline of the body and thus completing the second lobe of the Spanish guitar. The next stages in the transition are concerned with the addition of a neck and of frets. All these instruments are twanged by the fingers. One may conclude that the use of the bow was either unknown at this time (c. 6th century), or that it was still confined to instruments of the rebab type. The earliest known representation of a guitar fiddle complete with bow (fig. 2) occurs in a Greek Psalter written and illuminated in Caesarea by the archpriest Theodore in 1066 (British Library, Add. MS. 19352). Instances of perfect guitar fiddles abound in the 13th century MSS. and monuments, as for instance in a picture by Cimabue (1240–1302), in the Pitti Gallery in Florence.