6‑plus‑6 instruments: two‑row, whole‑tone/isomorphic keyboard layouts

Layout and fingering

In a typical 6‑plus‑6 layout each row advances by a whole step between adjacent keys; a note directly adjacent on the other row is a semitone away. This can be described succinctly: moving along a row changes pitch by a whole tone (whole tone), moving between rows moves by a half tone (half tone). Because of that regular interval pattern the same finger movements produce the same musical intervals whenever the starting note lies in the same row. If a third row repeats the pattern of the first row, the same fingering extends to all twelve starting pitches, creating a fully isomorphic keyboard.

History and examples

Designs that apply the 6‑plus‑6 idea appear in the history of alternative keyboards. A well‑known historic example is the Janko keyboard, which rearranged piano keys into a compact, regular grid so that common scale and chord patterns have consistent shapes; this and other experimental keyboards were proposed in the 19th and early 20th centuries to simplify technique. Modern experiments and some button instruments also use related two‑row or three‑row layouts; the 6‑plus‑6 principle is one way instrument builders have sought greater uniformity of fingering across keys (Janko keyboard).

Uses, advantages and limitations

• Advantages: consistent, repeatable fingering across many tonalities simplifies transposition and can speed learning of patterns and chords.
• Practical uses: useful in pedagogical instruments, experimental keyboards, and some free‑reed or button instruments where compact, regular layouts are valued.
• Limitations: departure from the familiar piano layout makes repertoire transfer and ensemble matching harder; manufacturing and adoption costs limited widespread use.

Related systems and notable facts

6‑plus‑6 keyboards are a subset of "isomorphic" keyboard designs: arrangements in which musical intervals have the same geometric shape regardless of pitch. Other isomorphic arrangements (for example, the Wicki‑Hayden or Harmonic Table families) use different patterns of intervals but share the goal of uniform fingering. The 6‑plus‑6 pattern is distinctive for its simple whole‑tone rows offset by a semitone, and for the way a duplicate third row can extend identical technique to every chromatic starting pitch.

For further reading on interval structure and keyboard design, see sources that describe whole‑tone and semitone relationships and historical keyboards such as the Janko system (whole tone, half tone, Janko keyboard).