Diamond-MOS notation

Diamond-MOS notation is a notation for MOS systems, which aims to avoid potential conflicts with diatonic notation by introducing a new set of symbols and attempting to make the MOS itself as easy to read as possible. Diamond-MOS notation replaces letters, clefs, accidentals, key signatures, and pitch correspondences with notes, while keeping all other aspects of diatonic notation the same.

Note names

Nominals

To avoid collision with diatonic notation (which uses letters from A to G, as well as H in some countries) and with the Roman numeral I, the starting letter for diamond-mos is J, which corresponds to C in standard notation and indicates the "middle note" and the start of the scale being referenced. The nominals continue JKLMNOPQRSTUVWXYZ, allowing for MOS scales with up to 17 notes (such as argent[17]) to be notated.

Accidentals

To avoid collision with diatonic notation, and to account for cases where the diatonic # and b accidentals may remain useful (such as in complexity-2 or -3 temperaments), the accidentals for a MOSchroma are @ (which lowers a note, i.e. "flat" = "at") and & (which raises a note, pronounced "am"). That way, J-M-P in blackwood major would be a major triad, and J-@M-P would be a minor triad. Any new accidental cancels all previous ones, similarly to ups and downs notation.

Diamond-mos notation may be combined with ups and downs notation in an edo, and when the moschroma is only 1 edostep, the up or down is often preferred. Otherwise, ups and downs may represent a specified subchroma.

The score

The heading

The MOS and its chosen mode and tuning are written at the top of a score notated in diamond-MOS. The mode is for the nominals on middle J, which is the same as middle C. So, to notate blackwood major in diamond-MOS, [15edo] [2-1-2-1-2-1-2-1-2-1] might be used (or a different edo that supports the scale, such as 25).

Clefs

Diamond-mos clefs indicate the location of middle J with the large diamond, and additional J notes with the smaller diamonds, indicating octaves. To the right of the diamonds, small boxes are placed to represent steps of the MOS - hollow boxes represent small mossteps and filled boxes represent large mossteps (think of a piano, where small diatonic steps have no black key in between, and large diatonic steps do). Note that the only steps marked are the kind which the MOS has fewer of (so ssLssssLss would be marked with two filled boxes and nothing else).

Key signatures

A diamond-mos clef and barline.

Key signatures follow similar rules to diatonic key signatures, indicating the number and location of alterations from the listed scale to a different one. For instance, to modify ssLssssLss on J to sssLssssLs, @ symbols are placed on the positions representing the third and eighth degrees of the scale. It is recommended, however, to simply write the transposition explicitly.

The staff

The staff is usually 5 lines. A larger staff (more than 5 lines) may be used in large MOSes. It is best for the staff to span at least one octave.

Interval names

Interval names are as in TAMNAMS, which is often integrated with diamond-MOS notation. Degrees use numerals similar to diatonic notation but zero-indexed (as in TAMNAMS) and with the @ and & accidentals. It is best to notate a chord by specifying each of its intervals, this avoids as much ambiguity as possible.

Readability features

These features originate in diamond-mos notation, but may be more generally applied outside of it.

• When using a staff with more than 5 lines, one of the staff lines should be bolded; this doesn't mean anything but it serves to act as a point of reference for sight-reading and to indicate that there are more than 5 staff lines.
• The clef boxes are repeated on every barline to aid sightreading, and on ledger lines.
• Transpositions are written explicitly, i.e. "1\11 higher than written", at the top of the score or at a key change.
• Key signatures may feature non-MOS alterations, placed after a vertical dotted line labelled "ALT" below it.