The short octave (broken octave) was a common device effectively increasing the keyboard compass of smaller instruments, without making them any physically larger.
There is often a moment of confusion when a modern player experiences a short octave for the first time, especially one like this instrument where the bottom two sharps are split to provide a front and back half.
This feature can be found in some of the spinet or harpsichord models.
For sample keyboard, it should be tuned as per below:
What is a Broken Octave Keyboard?
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A keyboard layout used in early pianos, harpsichords, and organs (mainly 16th–18th centuries).
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Instead of having every chromatic note in the bass, the lowest octave was “broken” or rearranged.
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Certain rarely used accidentals (like C♯, D♯, F♯ in the lowest octave) were omitted, and their keys were re‑tuned to play more useful bass notes (like C, D, E).
How It Works
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On a normal keyboard, the lowest octave goes: C – C♯ – D – D♯ – E – F – F♯ – G – G♯ – A – A♯ – B.
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On a broken octave keyboard, some of those black keys (and even some white ones) were “reassigned.”
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For example:
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The key that looks like E♭ might actually sound C.
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The key that looks like F♯ might actually sound D.
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This gave players access to the most harmonically important bass notes without needing a longer keyboard.
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Why It Was Used
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Space-saving: Early instruments were smaller, so this allowed a wider bass range without extra keys.
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Cost-saving: Fewer strings and less wood were needed.
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Musical practicality: In early music, low sharps/flats were rarely used, but low C, D, and E were essential.
Historical Context
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Common in Italian and Iberian harpsichords of the Renaissance and Baroque.
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Some early fortepianos also used it.
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By the late 18th century, as music became more chromatic and instruments grew larger, the full chromatic bass octave replaced the broken octave.
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