Universal key

The universal key or universal scale is a concept employed in music theory in which specific notes or chord symbols in a key signature are replaced with numbers or Roman numerals, so that the relationships between notes or chords can be universally applied to any key signature.

For example, in the key of E-flat major, the notes of the scale would be replaced like so:

• ETemplate:Music becomes scale degree 1
• F becomes scale degree 2
• G becomes scale degree 3
• ATemplate:Music becomes scale degree 4
• BTemplate:Music becomes scale degree 5
• C becomes scale degree 6
• D becomes scale degree 7

Triads (common practice style)

When used with chord symbols, the Roman numerals represent the root of a triad built on the associated scale step. In music theory based on the practices of the common practice period and its derivations the chord numerals are often written in upper case for chords in the major family, and in lower case for chords in the minor family, with the usual "m" or "—" minor chord quality suffix omitted outright:

• ETemplate:Music becomes I
• Fm⁷ becomes ii⁷
• Gm⁷ becomes iii⁷
• ATemplate:Musicmaj⁷ becomes IV maj⁷
• BTemplate:Music⁷ becomes V⁷
• Cm⁷ becomes vi⁷
• D^ø7 becomes vii^ø7

When representing the triads rooted in a minor key, the upper or lower case of the numerals indicate both its chord quality and that the key is minor:

• Cm⁷ becomes i⁷
• D^ø7 becomes ii^ø7
• ETemplate:Music becomes III
• Fm⁷ becomes iv⁷
• Gm⁷ becomes v⁷
• ATemplate:Musicmaj⁷ becomes VI maj⁷
• BTemplate:Music⁷ becomes VII⁷

A major drawback of using this method is its lack of use of accidentals. While in the numeric system, flats and sharps can be represented either by the use of fractions (e.g. an A natural in the scale above becomes 4+1⁄2) or, more commonly in written text, by inserting an accidental before the number (e.g. the same note becomes Template:Music5 or Template:Music4).

Triads (jazz and popular style)

In music theory aimed towards jazz and popular music, all triads are represented by upper case numerals, followed by a symbol to indicate if it is not a major chord (e.g. "m" for minor or "ø" for half-diminished):

• ETemplate:Musicmaj⁷ becomes I maj⁷
• Fm⁷ becomes IIm⁷
• Gm⁷ becomes IIIm⁷
• ATemplate:Musicmaj⁷ becomes IV maj⁷
• BTemplate:Music⁷ becomes V⁷
• Cm⁷ becomes VIm⁷
• D^ø7 becomes VII^ø7

When representing the triads rooted in a minor key, accidentals are used to indicate the chromatic alteration from the assumed major key roots indicated by numerals that don't have accidentals:

ETemplate:Music minor:

• ETemplate:Musicm⁷ becomes Im⁷
• Fm^ø7 becomes II^ø7
• GTemplate:Musicmaj⁷ becomes Template:MusicIIImaj⁷ (the assumed pitch for the root of a III numeral in ETemplate:Music is G, and the Template:Music is required to indicate that, in ETemplate:Music minor, this chord is rooted on GTemplate:Music)
• ATemplate:Musicm⁷ becomes IVm⁷
• BTemplate:Musicm⁷ becomes Vm⁷
• CTemplate:Musicmaj⁷ becomes Template:MusicVImaj⁷
• DTemplate:Music⁷ becomes Template:MusicVII⁷

This will frequently result in numerals whose accidentals are different than those of the actual root note, as they are referring to a change from the assumed pitch and not an absolute pitch:

D minor:

• Dm⁷ becomes Im⁷
• Em^ø7 becomes II^ø7
• Fmaj⁷ becomes Template:MusicIII maj⁷ (the assumed pitch for the root of a III numeral in D is FTemplate:Music, and the Template:Music is required to indicate that, in D minor, this chord is rooted on F)
• Gm⁷ becomes IVm⁷
• Am⁷ becomes Vm⁷
• BTemplate:Musicmaj⁷ becomes Template:MusicVI maj⁷
• C⁷ becomes Template:MusicVII⁷

Further reading

• Baxter, John (2010). Deluxe Encyclopedia Of Mandolin Chords, p. 11. Mel Bay. Template:ISBN.