# 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, and 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 the natural notes. 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.

**Equivalence** may arise from this approach. This is when you have multiple names for the same pitch. The equivalence that occurs in 12edo is **enharmonic equivalence**. C-sharp is enharmonically equivalent to D-flat, but only in 12edo, 24edo, 36edo, etc. The same term is sometimes used to refer to equivalence in general, but each edo technically has its own equivalence. 7edo has the type of equivalence that could be called *chromatic equivalence*, for example.

## 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

## See also

- Enharmonic (disambiguation page)