Why pairs of strings?
Because the lute’s ancestor, the oud, has pairs of strings, so does the lute retain this feature. The pairs of strings were likely an attempt to increase the volume of the instrument. The higher courses are unisons, or the same pitch, whereas the lower courses are strung in octaves, with the lower pitched string towards the bass side. The thumb or fingers must pluck the pairs that make up each course with considerable care or else the course will be sounded as two distinct notes. Although it is physically impossible to sound each string of a course at the same moment, the illusion can be successful with a good technique.
