Type: Chordophones > Lutes.
Hornbostel Sachs No#: 321.312.5
Description: The archlute [in Spanish archilaúd, in Italian arciliuto, in German Erzlaute, in Russian архилютня arkhilyutnya] It is a European plucked string instrument developed around 1600 as a compromise between the very large theorbo. The size and re-entrant tuning of which made for difficulties in the performance of solo music and the Renaissance tenor lute, which lacked the bass range of the theorbo. Essentially a tenor lute with the neck-extension of the theorbo, the archlute lacks the power in the tenor and the bass that the large body and typically greater string length provide.
The main differences between the archlute and “baroque” lutes of Northern Europe are that the baroque lute has 11 to 13 courses. While the archlute typically has 14 and the tuning of the first six courses of the baroque lute outlines a d-minor chord, while the archlute preserves the tuning of the Renaissance lute, with perfect fourths surrounding a third in the middle for the first six. The archlute was often used as a solo instrument for the first three-quarters of the 17th century, but is rarely mentioned as a continuo instrument in this period, the theorbo being the lute class instrument with this role.
As continuo bass lines were composed both faster in motion and higher in tessitura towards the end of the 17th century, the archlute began to eclipse the theorbo as the main plucked string continuo instrument. The theorbo lacked the higher notes of the bass lines and the increasing practise of doubling the continuo part with a bowed bass [cello or viol] made the archlutes’ lack of power in the tenor and bass a less important shortcoming.
The theorbo had been commonly used as the melodic bass instrument in trio sonatas from the beginning of the Baroque and the archlute took over that function too, with the most famous example being Corelli’s Opus 1 and 3 trio sonatas which have part-books for 1st and 2nd violin, ‘violone o arciliuto’ and a continuo part for organ, a simplified version of the ‘violone o arciliuto’ book. The violone o arciliuto book has just as many figures to tell the player what chords to play as the organ part-book, which suggests the archlute player would be adding chords above the bass where possible.
The archlute was used in Handel’s operas and like repertoire; Giulio Cesare  has continuo parts labelled both arciliuto and tiorba. Perhaps one player would play both instruments.
Citations: Bibliography: Websites: Chitarrone, Theorbo and Archlute by Robert Spencer ;