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Short octave
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The short octave was a method of assigning notes to keys in early
keyboard instruments (harpsichord, clavichord, organ), for the purpose of giving the instrument an extended range in the bass. A closely related system, the broken octave, is covered below.
The short octave
In one variant of the short octave system, the lowest note on the keyboard was nominally E, but the pitch to which it was tuned was actually C.
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Encyclopedia
The short octave was a method of assigning notes to keys in early
keyboard instruments (harpsichord, clavichord, organ), for the purpose of giving the instrument an extended range in the bass. A closely related system, the broken octave, is covered below.
The short octave
In one variant of the short octave system, the lowest note on the keyboard was nominally E, but the pitch to which it was tuned was actually C. Nominal F# was tuned to D, and nominal G# was tuned to E. Thus, in playing the keys:
E F# G# F G A B C
the player would hear the musical scale of C major in the bass:
C D E F G A B C
The actual note assignments can be seen in the following diagram, which shows the lowest eight keys of an early keyboard.
The rationale behind this system was that the low notes F# and G# are seldom needed in early music. Deep bass notes typically form the root of the chord, and F# and G# chords were seldom used at this time. In contrast, low C and D, both roots of very common chords, are sorely missed if a harpsichord with lowest key E is tuned to match the keyboard layout.
A second type of short octave used the following keys:
B C# D# C D E F# G
to play the G major scale
G A B C D E F# G
Here, the "exotic" bass notes C# and D# are sacrificed to obtain the more essential G and A.
In stringed instruments like the harpsichord, the short octave system created a defect: the strings which were tuned to mismatch their keyboard notes were in general too short to sound the reassigned note with good tone quality. To reach the lower pitch, the strings had to be thickened, or tuned too slack. During the 17th and 18th centuries, harpsichord builders gradually increased the size and bass range of their instruments, to the point where every bass note could be properly played with its own key.
Short octaves were also sometimes used in the organ. Here, the practice would not have yielded poor tone quality (since the associated pipes would have to be built with the correct length in any event); nevertheless, because of the loss of musical flexibility they entailed, short octaves ultimately came to be abandoned in organs as well.
The broken octave
A variant of the short octave added more notes by using split keys: the front part and the back part of the (visible) key controlled separate levers and hence separate notes. Assume the following keys:
E F F# G G# A
with both F# and G# split front to back. Here, E played C, the front half of the F# key played D, and the (less accessible) rear half played F#. The front half of the G# key played E, and the rear half played F#. As with the short octave, the key labeled E played the lowest note C. Thus, playing the nominal sequence
E F# (front) G# (front) F F# (back) G G# (back) A
the player would hear:
C D E F F# G G# A
The actual note assignments can be seen in the following diagram.
It can be seen that only two notes of the chromatic scale, C# and D#, are missing. An analogous arrangement existed for keyboards with G instead of C at the bottom.
According to Trevor Pinnock (reference below), the short octave is characteristic of instruments of the 16th century. He adds, "in the second half of the 17th century, when more accidentals were required in the bass, 'broken octave' was often used."
The Viennese bass octave
The short/broken octave principle not only survived, but was even developed further in one particular location, namely Vienna. The "Viennese bass octave" (German: "Wiener Bass-oktave") lasted well into the second half of the 18th century. Gerlach (2007) describes this keyboard arrangement as follows:
- The notes leading down to F1 were accommodated on the keys of a "short-scaled octave" from c to C (only F#1 and G#1, as well as C# and Eb continued to be omitted.
The assignment of notes to keys, which strikingly included a triple-split key, was as shown in the following diagram, adapted from Maunder and Maunder (1998):
Maunder and Maunder (who use the term "multiple-broken short octave") observe that the Viennese bass octave, like its predecessors, imposed distortions on the string scaling of the harpsichord: it "leads to extreme foreshortening of the scale in the bass." Hence, it required unusually thick strings for the bottom notes, on the order of 0.6 to 0.7 mm.
Joseph Haydn may be the most best known composer who wrote for the Viennese short octave (his works for keyboard were intended for harpsichord, not piano, until the early 1770s).. His "Capriccio in G on the folk song 'Acht Sauschneider müssen sein'", H. XVII:1 (1765), is clearly written for a harpsichord employing the Viennese bass octave, as Gerlach (2007) points out. The work terminates in a chord in which the player's left hand must cover a low G, the G an octave above it, and the B two notes higher still. On orthodox keyboards this would be an impossible stretch for most players, but as on the Viennese bass octave it would have been easy to play, with the fingers depressing keys that visually appeared as D/G/B (see diagram above).
The Viennese bass octave gradually went out of style. When Haydn's Capriccio was published by Artaria in the 1780s, the publisher included alternative notes for the places where the original version could be played only on a broken octave instrument, presumably to accommodate the needs of purchasers who owned a harpsichord or piano with the ordinary chromatic bass octave. However, Maunder and Maunder note instruments with Viennese bass octave built even in 1795, and observe that advertisements for such instruments appear even up to the end of the century.
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