Home : Theory and Patterns : Roman Numerals
Roman numerals are used to define every possible chord progression that
can occur in a piece of music.  They're used to change songs from one
key to another, to figure out songs by ear, to write and improvise
music from scratch, and in general to understand how characteristic
harmonic sounds occur in every type of music.  
To understand why roman numerals are useful, it's important to
understand that they're simply a way of notating chord progressions.
Chords themselves are basically a shorthand way of simply defining the
groups of notes that make up a piece of music.  They don't provide any
melodic information, but they tell you the groups of notes from which a
melody comes, and the notes that can be used to accompany any given
melody.  Roman numerals are an even more fundamental way of notating
chord progressions within a key.  They provide the most useful and
practical way of understanding and hearing how chords are grouped
together to make up common harmonic progressions.  Professional
musicians often use roman numeral labels such as "I IV and V", instead
of chord names such as "G C and D" to speak about which chords and note
groups make up a piece of music.  This guide will teach you how to
convert roman numerals to bar chords on the guitar fretboard.
Roman Numerals tell you the same things that chord labels tell you:
the root note (letter/fret position) of a chord and the sonority
(shape) of the chord.   There are 7 roman numerals used in music:
        1    2    3    4    5    6    7
Large:  I    II   III  IV   V    VI   VII
Small:  i    ii   iii  iv   v    vi   vii
The numbers are laid out on the fretboard as follows (this finger
pattern can be moved to any fret):
starting on the     starting on the
6th string:         5th string:
______              ______
||||||              ||||||
7|||||              4|||||
14||||              |7||||
||||||              51||||
25||||              ||||||
||||||              62||||
36||||              ||||||
||||||              |3||||
||||||              ||||||
______              ______For example, the numbers in the key of G (starting on the note G) are:
starting on the     starting on the
6th string:         5th string:
______              ______
||||||              ||||||
F#||||              C|||||
GC|||| 3rd fret     |F#|||
||||||              DG|||| 10th fret
AD||||              ||||||
||||||              EA||||
BE||||              ||||||
||||||              |B||||
||||||              ||||||
______              ______
1=G, 2=A, 3=B, 4=C, 5=D, 6=E, 7=F#
(G is at the 3rd fret of the 6th string, and at the 10th fret of the
5th string.)
The numbers in the key of C (starting on the note C) are:
starting on the     starting on the
6th string:         5th string:
______              ______
||||||              ||||||
B|||||              F|||||
CF|||| 8th fret     |B||||
||||||              GC|||| 3rd fret
DG||||              ||||||
||||||              AD||||
EA||||              ||||||
||||||              |E||||
||||||              ||||||
______              ______
1=C, 2=D, 3=E, 4=F, 5=G, 6=A, 7=B
(C is at the 8th fret of the 6th string, and at the 3rd fret of the 5th
Below are the notes on each string, to help assign letters (chord
names) to roman numeral progressions:
Fret #:      0 1  2  3 4  5 6  7 8 9  10 11 12  
6th string:  E F  F# G G# A Bb B C C# D  Eb E
5th string:  A A# B  C C# D Eb E F F# G  G# A
The notes on every string start over at the 12th fret (the note on the
12th fret is the same as the open string, the note at the 13th fret is
the same as the 1st fret, the note at the 14th fret is the same as the
2nd fret, etc.)IMPORTANT:  as shown above, the number indicated by a roman numeral
tells you the root note (letter) of the chord to play.  The type of
roman numeral written tells you type of chord to play:
-  A large roman numeral means play a MAJOR chord.
-  A small roman numeral means play a MINOR chord.
-  A large roman numeral with a 7 means play a 7th ("dominant") chord.
If the number (roman numeral) is on the 6th string, use an "E" shape
(E, Em, or E7):
      E major  E minor    E7
Bar:  ++++++   ++++++   ++++++
      |||+||   ||||||   |||+||
      |++|||   |++|||   |+||||
      ||||||   ||||||   ||||+|
If the number (roman numeral) is on the 5th string, use an "A" shape
(A, Am, or A7):
      A major  A minor    A7
Bar:  ++++++   ++++++   ++++++
      ||||||   ||||+|   ||||||        
      ||+++|   ||++||   ||+|+|        
      ||||||   ||||||   ||||||
I   in the key of G = G major (large roman numeral on the 1st note in
the G scale)
vi  in the key of C = A minor (small roman numeral on the 6th note in
the C scale)
V7  in the key of C = G 7th (large roman numeral with a 7, on the 5th
note in the C scale)
IMPORTANT:  any other chord type can be labeled with a roman numeral -
just add the chord type to the roman numeral (Imaj7#11=Cmaj7#11 in the
key of C).  The only difference between using roman numerals and letter
names to label chords is that letters are replaced by the roman numbers
within a key, as described above (ie., relative to a starting note).
By doing that, every potential chord progression moves within the
framework of a key note.   Using that point of reference, it becomes
clear that all chord progressions form recognizable patterns and move
in simple, predictable ways.  This makes learning songs, playing by
ear, composing, improvising, and understanding every potential harmonic
sound in music a much simpler process.-------------------------------------------------------------
Chords are grouped into several categories:  diatonic, borrowed,
secondary dominant, and blues.  Each category produces familiar
harmonic sounds.
Diatonic chords are used in virtually every type of music.  They are
most common in traditional, folk, classical and pop music.  The I IV
and V(7) chords are used in virtually every piece of music you hear,
regardless of style.  Learning those three chords in every key is
fundamental to understanding and recognizing chord patterns of every
     I  ii  iii  IV  V(7)  vi   (V can be either major or 7th)
G:   G  Am  Bm   C   D  Em
A:   A  Bm  C#m  D   E  F#m
C:   C  Dm  Em   F   G  Am
      I           V(7)                   I                       IV   
Happy Birthday to you. Happy birthday to you. Happy Birthday (Whoever).
      I        V  I
Happy Birthday to you.
BORROWED CHORDS - flats mean move the chords down 1 fret:
Borrowed chords are used heavily in rock music.  You'll see them used
regularly with distorted guitar sounds in heavy mainstream pop music.
You'll also see them used in bluegrass and other model styles.
     bVII  bIII  bVI  (bV  bII)
G:   F     Bb    Eb   (Db  Ab)
A:   G     C     F    (Eb  Bb)
C:   Bb    Eb    G    (Gb  Db)
     iv  (usually used in a   IV  iv  I   progression)
     v   (usually used in a   v   I7  IV  progression)SECONDARY DOMINANTS:
Secondary dominant chords are 7th (also 9th, 11th, and 13th dominant)
chords that come from other keys ("secondary keys").  They create an
interesting, unexpected harmonic "twist" - a bit of temporary harmonic
tension when added to a chord progression.  You'll see secondary
dominants most in jazz and classical music, but also in pop ballads
that have a "playful" sound.
     I7   II7   III7   VI7    VII7
Blues are basically defined by dominant 7th (also 9th, 11th, and 13th)
chords on the numbers I, IV, and V.  You'll see them most in bluesy
music :)
     I7   IV7    V7
Minor chord progressions tend to sound sad, dark, and more serious than
other types of chord progressions.  To create a minor chord
progression, just START and end on the vi chord, and use any of the
chords from other categories to form a progression.  Minor chord
progressions typically contain the secondary dominant "III7" chord -
that chord helps to create a harmonic focus on the vi chord.
I     IV    I     V
I     vi    IV    V7
I     iii   IV    V
vi    IV    ii    V
I     V     IV    V
I     IV    I     V
I     ii    iii   IV    V
I     iii   vi    ii    V
I     bVII  IV    IV
I     IV    bVII  V7
I     bVII  bIII  II     ii    bIII  I
I     bVI   bVII  I
I     bIII  IV    bVI   bVII
I     bII   bV    V
I     iii   IV    iv
Secondary Dominant:
I     I7    IV    iv
I     III7  vi    IV
I     ii    III7  IV
I     vi    II7   V7
I     VII7  iii   III7  vi   VI7  II7  IV
I     VI7   II7   V7
I     iii   II7   IV
I7  IV7  I7   I7    IV7  IV7  I7  I7  V7  IV7  I7  V7
I7  IV  I  I7  IV  #IVdim7  I   ii   iii  bIII  ii  V7  I
Minor (just start on vi):
vi    V7    IV    III7
vi    IV    ii    V
vi    ii    V     I     IV   VII7 iii  III7
vi    iii   ii    III7

Copyright 2004-2013 Nick Antonaccio, all rights reserved.