Figure 2. An octave span of the two manuals of the archicembalo. In (a-c), ascending from the bottom of the figure, a cumulative display of the logical components of the 19-key lower manual: (a) the usual 12-note meantone gamut; (b) split keys on every black note provide alternative accidentals; (c) new keys between E–F and B–C extend the chain of 5ths sharpwards from Asharp. In (d), at the top of the figure, the 17-key upper manual is depicted, with arrows indicating its ascending circle-of-5ths connections to and from the lower manual; despite their spelling, these 5ths between manuals (Bsharp–Ġflat and Ḃ–Gflat) are as good as all the others. The upper manual covers pitches between Ġflat (= Fdouble-sharp) to Ḃ (= Cflat) in the circle of 5ths; the remaining five pitches on the split keys (unlabeled here) would be tuned as pure 5ths relative to the lower manual.