The enharmonic keys used in practice are:—
B (five sharps) enharmonical to Cb (seven flats)
F# (six sharps) enharmonical to Gb (six flats)
C# (seven sharps) enharmonical to Db (five flats)
Rule 4. The Sum of the Enharmonic Flat and Sharp Signatures is Twelve. Notice that this is true in the above three keys.
By this rule the theoretical keys (that is, those having more than seven sharps or flats) are easily found. For example:—to find the key having eleven flats; the key having eleven flats is enharmonical to the key having one sharp (11 + 1 = 12). G has one sharp and changing its name to the enharmonic flat key, we obtain Abb which, therefore, has eleven flats. This process should be applied to all keys having eight to eleven sharps and eight to eleven flats inclusive.
As stated in the first chapter, the pitch of a tone is determined by the note's position on the staff. The staff of five lines with its spaces allows of the designation of but one octave and one step, whereas, in modern music, there is need of the notation of at least six octaves. This necessitates the use of symbols called clefs, and lines added to the staff called ledger lines. Ledger lines are short lines parallel to the staff lines added above or below the staff lines.
There are three clefs:—
1. the treble or G clef,
2. the tenor, movable or C clef,
3. the bass or F clef.
Middle C is the tone which all voices can sing. It is in the lower register of the high female voice and in the upper register of the low male voice.
The G clef (treble clef) is for high voices or instruments. Its symbol shows the position of the G next above middle C thus: