This is a treble viol or vihuela de arco based on a wall painting in Knights' Hall of Goldegg Castle in the Pongau area (1536).
These paintings are atributed to Hans Bocksberger the older together with other painters. His style contains German elements (A. Dürer) as well as Italian characteristics (Renaissance, Mannerism).
He might have learned with his father and perhaps made some learning years in Italy, anyhow had he exact knowledge of Italian style elements of the time.
His style points both German elements (Albrecht Dürer), and Italian elements (Renaissance and Mannerism).
One of the characteristical features of this instrument is the bridge.
The treble leg goes down (we suppose) on to the back trough a hole on the soundboard. This makes the sound closer to an instrument with a soundpost (sth like a viol or a violin) even though the treble string is slightly unbalanced, gives a weaker sound than the rest (At least in this case, where there is no longitudinal bar or thickening of the soundboard).
This kind of bridge/soundpost is also depicted 'on the title pages of the superius, altus and bassus part books of the copies in theBasel Universitätsbibliothek of 'Reutterliedlin' printed by Christian Egenolph in Frankfurt am Main (1535)' (below) according to E. Segerman in his article The development of European bowed instruments
foto: Heinz Kaiser, Kulturverein SCHLOSS GOLDEGG
This instrument shares some features with the vihuela de mano.
It has been built on a board using no mould.
The ribs are inserted in the neck, which goes inside the body and works as a top block.
It has no corner blocks and the joints are reinforced with linen strips. Soundboard is glued on ribs using no linings at all.
The neck in not angled backwards, it is in the same plane as the soundboard. To get the string height, the fingerboard is wedge shaped, giving a thick neck close to the body joint as we can see in the painting.
The soundboard is flat with two small transversal bars aligned with the corners.
Dimension of the instrument have been taken based on a reference, in this case the distance between the eye centers (or interpupillary distance). This way measuring can be 'accurate' providing that the reference measure and the object to be measured are on the same plane. In this case they are not on the exact same plane, so the size of the instrument is not exactly what it is represented on the painting. There is also the fact of the 'loose' accuracy when depicting this instrument. We can see much greater detail on the instrument on the right than on the rest.
The tuning choosen for this instrument has been g c' e' a' d'' taken from the Munich University Library 4º Cod, ms. 718 dated (1523/4) which comes to be the same as Gerle gave in his Musica Teusch (Nuremberg 1532).