The universal key or universal scale is a concept employed in music theory

Music theory

Music theory is the study of how music works. It examines the language and notation of music. It seeks to identify patterns and structures in composers' techniques across or within genres, styles, or historical periods...

 in which specific notes

NOTES

Natural orifice transluminal endoscopic surgery is an experimental surgical technique whereby "scarless" abdominal operations can be performed with an endoscope passed through a natural orifice then through an internal incision in the stomach, vagina, bladder or colon, thus avoiding any external...

 or chord symbols in a key signature

Key signature

In musical notation, a key signature is a series of sharp or flat symbols placed on the staff, designating notes that are to be consistently played one semitone higher or lower than the equivalent natural notes unless otherwise altered with an accidental...

 are replaced with numbers or Roman numerals

Roman numerals

The numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...

, allowing for a discussion describing relationships between notes or chords that can be universally applied to all key signatures.

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

• E becomes scale degree 1
• F becomes scale degree 2
• G becomes scale degree 3
• A becomes scale degree 4
• B 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

Roman numerals

The numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...

 represent the root

Root (chord)

In music theory, the root of a chord is the note or pitch upon which a triadic chord is built. For example, the root of the major triad C-E-G is C....

 of a triad built on the associated scale step. In music theory based on the practices of the Common Practice Period

Common practice period

The common practice period, in the history of Western art music , spanning the Baroque, Classical, and Romantic periods, lasted from c. 1600 to c. 1900.-General characteristics:...

 and its derivations the chord numerals are often written in upper case for chords in the major

Major chord

In music theory, a major chord is a chord having a root, a major third, and a perfect fifth. When a chord has these three notes alone, it is called a major triad...

 family, and in lower case for chords in the minor

Minor chord

In music theory, a minor chord is a chord having a root, a minor third, and a perfect fifth.When a chord has these three notes alone, it is called a minor triad....

 family, with the usual "m" or "—" minor chord quality suffix

Chord names and symbols (jazz and pop music)

Various kinds of chord names and symbols are used in different contexts, to represent musical chords. In jazz and popular music, a chord name and the corresponding symbol are typically composed of one or more of the following parts:# The root note ....

 omitted outright:

• E becomes I
• Fm⁷ becomes ii⁷
• Gm⁷ becomes iii⁷
• Amaj⁷ becomes IV maj⁷
• B⁷ 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
• E becomes III
• Fm⁷ becomes iv⁷
• Gm⁷ becomes v⁷
• Amaj⁷ becomes VI maj⁷
• B⁷ becomes VII⁷

A major drawback of using this method is its lack of use of accidental

Accidental

Accidental may mean:* Accidental * Accidental , by Fred Frith* Accidental , a biological phenomenon more commonly known as vagrancy* Accidental property, a philosophical term-See also:* Accident...

s. 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 4½) or, more commonly in written text, by inserting an accidental before the number (e.g. the same note becomes 5 or 4).

Triads (Jazz and popular style)

In music theory aimed towards jazz and popular music

Jazz harmony

Jazz harmony is the theory and practice of how chords are used in jazz music. Jazz bears certain similarities to other practices in the tradition of Western harmony, such as many chord progressions, and the incorporation of the major and minor scales as a basis for chordal construction, but...

, all triads are represented by upper case numerals, followed by a symbol to indicate if it is not a major chord (e.g. "-" for minor or "ø" for half-diminished):

• Emaj⁷ becomes I maj⁷
• F -⁷ becomes II -⁷
• G -⁷ becomes III -⁷
• Amaj⁷ becomes IV maj⁷
• B⁷ becomes V⁷
• C -⁷ becomes VI -⁷
• 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:

E- (minor):

• E -⁷ becomes I -⁷
• Fm^ø7 becomes II^ø7
• Gmaj⁷ becomes IIImaj⁷ (the assumed pitch for the root of a III numeral in E is G, and the is required to indicate that, in E-, this chord is rooted on G)
• A -⁷ becomes IV -⁷
• B -⁷ becomes V -⁷
• Cmaj⁷ becomes VImaj⁷
• D⁷ becomes VII⁷

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):

• D -⁷ becomes I -⁷
• E -^ø7 becomes II^ø7
• F maj⁷ becomes III maj⁷ (the assumed pitch for the root of a III numeral in D is F, and the is required to indicate that, in D-, this chord is rooted on F)
• G -⁷ becomes IV -⁷
• A -⁷ becomes V -⁷
• Bmaj⁷ becomes VI maj⁷
• C⁷ becomes VII⁷