The terz guitar
The terz guitar comes by other names too, all of which reflect its tuning of a minor third up on the classical guitar.
What other names? Names such as tierce and tertz, or even the confusing "third guitar" - especially confusing if there are only two guitars in the room... Then again, no more confusing than calling the third hand on a watch "the second hand".
Famous guitar composers such as Giuliani included the terz guitar in their works.
Unlike the Niibori guitars, which are, if you refer to the pitch of the top string, one key sharper than the classical guitar (being B instead of E), the terz is three keys flatter (being G instead of E). This means that a terz/classical guitar duo plays in two widely different keys, a typical example being a duet in which the guitar is in C (no sharps) and the terz is in A (3 sharps). That's to say, the terz needs a key signature with three more sharps than a guitar when played alongside it.
Those who believe that guitars sound brighter in the sharp keys because of the preponderance of open strings might feel that this is another reason why the terz had a reputation for being an instrument that carried well.
Much music was composed or arranged for the terz in the 19th century, and Vienna was a particular hot-spot for the instrument.
In common with all short-neck small bodied guitars, the terz has an apparent power of projection that is due partly to the higher pitch and partly due to the preponderance of upper harmonics.
Nowadays, it is relegated to the sidelines of the guitar orchestra because the set of comfortable keys available to both terz and classical guitars in a duet is very much less than the choices available to alto and classical, and of course the alto offers even more range above the classical guitar than does the terz.