# Nominal-accidental chain

*"Sharp" and "flat" redirect here. For the temperaments, see Sharp (temperament) and Flat (temperament).*

This is a neologism for the common pattern in notating microtonal pitch systems. These are analogous extensions of basic Western musical notation.

**Nominals** are pitch elements that have specific names. In Western musical notation, these names are the seven letters A B C D E F G (historically, H has also been used). In a pentatonic notation, there would be only five names.

**Accidentals** are additional pitches that arise as modifications of the nominals. Unmodified pitches are natural notes. In diatonic circle-of-fifths notation, the additional pitches are denoted by adding **sharps** or **flats** to A-G. The sharp accidental denotes a pitch raise by a chromatic semitone, equivalent to a raise by 7 fifths minus 4 octaves. Conversely, the flat accidental denotes a pitch drop by the same amount. In equal temperaments, the number of steps this interval is mapped to is called the sharpness.

These pitches form a chain, with each one separated from the next by a specific interval. This interval can be said to generate the notation, or the notation can be said to be based on this interval. In diatonic circle-of-fifths notation, this interval has been a just or near-just 3/2. Other intervals are possible, and even desirable for certain edos like 13, 18 and 23.

**Enharmonic equivalence** may arise from this approach. This is when you have multiple names for the same pitch. C-sharp is enharmonically equivalent to D-flat, but only in 12edo, 24edo, 36edo, etc.

## Specific notation schemes

- Diatonic

- Circle-of-fifths notation (and neutral circle-of-fifths notation)

- Nondiatonic

- Bohlen-Pierce notation (based on the lambda scale)
- Armodue number notation (based on the superdiatonic scale)
- Fox-Raven notation (based on the oneirotonic scale)
- Arcturus hendecatonic notation (based on the Arcturus[11] scale)
- Diamond-mos notation

- Unsorted

- Erv Wilson's greek letters
- Aaron Hunt's system

## Related topics

- The term "albitonic"
- Mark Gould's connection of accidentals to bi-level MOS