In RealLife, gitterns were a medieval/Renaissance instrument, similar to a lute, and plucked, which Elanthia is consitant with. However, the gittern was popular more in the fourteen and fifteen hundreds, up until it was surpased by the lute. In Elanthia, the gittern is supposedly a much more complex instrument, with twelve strings. In RealLife, the gittern was an instrument of lesser complexity to the lute, having most commonly only four strings to the lute's normal six.
So, according to GMs, a gittern is one of the hardest instruments to play, even though it should really be easier than a lute, and the lute should be much higher up there. And have no cap. But there you go.
Gitterns are currently only available from Malik the True Bard's Instruments and Picks, southwestern Shard, Illithi, with the following customizations: