There are two ways to construct an Italian harpsichord, both of which are found in the historical tradition:
Many historical instruments retuned the lowest notes to provide bass notes a third lower than the letter names usually given to those keys. On the Trasuntino, the lowest note BB plays GG, the C# plays AA and the D# plays BB (this is called the GG/BB short octave). On the F.A., the lowest note E plays C, the F# plays D and the G# plays E (this is called the C/E short octave). These substitutions allow common bass notes to be played without enlarging the instrument in the bass region. The notes can always be tuned to their usual pitches instead, if the player so desires, although retuning too often will eventually break the strings due to metal fatigue.
The keyboard range of these instruments can be extended, at additional cost, to provide extra notes in the treble and bass, eliminating the need for a short octave and enlarging the repertoire that can successfully be performed.
All harpsichords come with a keyboard that can be shifted one position to allow performance at a pitch of A=440 Hz (the modern standard) or A=415 Hz (so-called "Baroque pitch").