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Musical Architectures

Modes, Intervals and Scales

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This page covers the musical architectures common to American and Irish folk music. For Arabic and Turkish music, see:


Intervals refer to the difference in pitch between notes, whether the notes are played together (as a chord) or in sequence, one after the other. Each type of scale or mode is composed of a unique combination of intervals. These combinations provide the feeling associated with that type of scale or mode.

Interval sizes in Western music increment by half-steps (or SEMI-TONES) and are frequently demonstrated on a piano keyboard.

Looking at the diagram at the right: every movement from one key to the very next key is a half step (1/2). If you start on a black key, any movement, left (down) or right (up) to the next key is to a white key. If you start on a white key, you will usually end up on a black key.

Much of our emotional response to music is tied to the intervals between notes. Play both ends of an interval at once and you hear a chord. Play the ends in sequence and you have part of a tune. Both invoke feeling in many people. This association of feelings with intervals is built over a lifetime, which is why Western people listening to Middle Eastern or Eastern music, which includes intervals that we are not familiar with, frequently describe what they hear as wailing cats.

"Two notes are described as being enharmonic when they refer to the same pitch: C# and Db are enharmonic, as are F# and Gb. At least they are these days. They weren't before the time of Bach." —Simon Bennett.

"Well, for instance, a perfect third is about 15 cents flat of equal temperament. If you were to play a third on a piano, it sounds aweful. A third is about 15 cents flat, a fourth is close enough, a fifth is close enough, a sixth is about 11 cents flat again – but you can do all that [play perfect intervals, rather than equal temperament] on a fiddle, and you can't do it on a fixed pitch instrument." —Caoimhin O Raghaillagh

Interval Steps Interval Steps
Minor 2nd ½ Major 2nd 1
Minor 3rd Major 3rd 2
Perfect 4th    
Diminished 5th 3 Perfect 5th
Minor 6th 4 Major 6th
Minor 7th 5 Major 7th
Octave 6    
Octave diagram using piano keyboard

"[An interval which is exactly half the width of an octave is] called by various names: the tritone, the diminished fifth, and the augmented fourth are three of its most common names. To hear this interval in action, play a C and an F# at once. It's a bit floaty and spooky, isn't it? The clergy used to call it diabolus in musica and all but banned its use in religious music." — Simon Bennett

Scales are built from Intervals

DIATONIC SCALEs are seven-note scales (not counting the repeating note at the top). Major scales, Minor scales, and Modes are diatonic. The seven pitches of any diatonic scale can be obtained using a chain of six perfect fifths. diatonic scale can be also described as two tetrachords (two perfect fiourths containing 5 semitones each) separated by a whole tone.


Major scales are the workhorse of Western music. They are constructed with the same intervals as a series of eight white keys on a piano, starting at C.
 Steps   C major   E major   
(Do - Re)WholeC to DE to F#
(Re - Mi)WholeD to E F# to G#
(Mi -Fa)Half E to FG# to A
(Fa - Sol)WholeF to GA to B
(Sol - La)WholeG to AB to C#
(La - Ti)WholeA to BC# to D#
(Ti - Do)Half B to C D# to E

Or, in shorthand; W - W - H - W - W - W - H. If you start on any piano key, white OR black, and use these intervals you will be playing a major scale.


Minor scales are also a workhorse of Western music. What makes a scale major or minor is triggered by state of the third: Two whole tones between the root and the third note, the scale is major; a whole and a half tone = minor.

Natural minor keys are constructed with the same intervals as a series of eight white keys on a piano, starting at A. Or, in shorthand; W - H - W - W - H - W - W. If you start on any piano key, white OR black, and use these intervals you will be playing a natural minor scale.

 Steps   A minor   C minor   C Harmonic minor
(Do - Re)WholeA to BC to DC to D
(Re - Ri)Half B to C D to EbD to Eb
(Ri - Fa)WholeC to DEb to FEb to F
(Fa - Sol)WholeD to E F to G F to G
(Sol - Si)Half E to FG to AbG to Ab
(Si - La)WholeF to GAb to Bb*Ab to B
(La - Do)WholeG to ABb to C*B to C

*The Harmonic minor is also frequently used. This is constructed by enlarging the interval between the 6th and seventh note by half a step and diminishing the interval between the seventh and eighth tone by a half step.

In short: Natural minor intervals are W - H - W - W - H - W - W.
Harmonic minor intervals: W - H - W - W - H - WH- H.


The combination of intervals that form each mode are based on the white keys of a piano. Ionian mode has the same intervals as found if you start on C and go up to C: whole step to D, whole step to E, half-step to F, whole step to G, whole step to A, whole step to B, half-step to C. Dorian intervals are those found if you start on D and go up to D. And so on.

Any starting note can be chosen. Every key signature can generate seven possible modes. Using the model of the white keys of a piano assists with visualization of the intervals, but some of the notes within many modes are going to be sharps or flats.

ModeBegins onIntervals
Ionian* Do W W H W W W H . . . . . .
Dorian Re . W H W W W H W . . . . .
Phrygian Mi . . H W W W H W W . . . .
Lydian Fa . . . W W W H W W H . . .
Mixolydian So . . . . W W H W W H W . .
Aeolian** La . . . . . W H W W H W W .
Locrian Ti . . . . . . H W W H W W W

*Ionian = major scale, **Aeolian = minor scale. These modes survived the historical transition from modes to scales in art music.

The charts illustrate why it can be difficult for musicians who are used to thinking in terms of major keys to jam with a folk musician whose repertoire centers around modal music. A key signature of F# and C# means D major to a Western musician, with D the tone that serves as the tonic the tune will resolve to. But in the Irish and Appalachian music world, a key signature of F# and C# often means a mode of A Mixolydian, with the tune resolving to A.


Gapped scales are scales containing only five, or sometimes six, notes in the octave, instead of the seven with which we are familiar in Western art music.

Western art music is based on a 7-note octave with the notes spaced at whole and half steps in specfic patterns. Pentatonic scales (5-note octaves) include two one-and-a-half-step intervals and hexatonic (6-note octaves) scales have one such interval. Pentatonic scales form the backbone for traditional music all over the world.

The most common pentatonic construction in Western music is built on a circle of fifths. The 4th and the 7th scale degrees are skipped. This would correspond to Mode 3 in Cecil Sharp's Pentatonic Modes chart. Mr Sharp identified FIVE pentatonic scale patterns in use in Appalachian songs at the turn of the 20th century.

Using the piano keyboard as a visual reference: Major pentatonic scales have the same intervals as the five black keys in an octave on the piano, starting on the F#. If you can transpose the tune so that it can be played on the black keys, then the scale is Pentatonic.

C   D   E   G   A   C
  W   W   WH   W   WH  

Another Pentatonic construction: Use the same intervals as those that result when omitting the third and seventh degrees of the C major scale. This construction is the one documented in Sharpe's book on Appalachian music.

C   D   F   G   A   C
  W   WH   W   W   WH  

Minor pentatonic, skipping the 2nd and 6th scale tone of the natural minor.

C   Eb   F   G   Bb   C
  WH   W   W   WH   W  
  Bb + Eb Bb    None  F#    F# + C# F# + C# + G#  
Ionian Bb F C G D A Hey Jude
Ring of Fire
Dorian C G D A E B Cluck Old Hen
Scarborough Fair
Phrygian      Sketches of Spain
Lydian      Dreams
Jane Says
Mixolydian    F C G D A E Old Joe Clark
Betty Liken.
Aeolian G D A E B F# Black Nag jig
Bonaparte Crossing the Rocky Mountains.
Locrian      Three Fantastic Dances
—Original chart from Fiddler Fakebook by David Brody.

The chart on the left demonstrates the interval organization of the various modes. Ionian mode has the same internal organization as Western Major keys; starting with the tonic note (which can be any note) one jumps a whole step, another whole step, a half, three more whole steps and and then a half to reach the tonic one octave above the starting one. The Ionian mode that starts with C uses all the white keys on the piano and none of the black, which is why it is so often used as an example. Try it yourself: W step from c to D, W to E, H to F, W to G, W to A, W to B, H to C.

"[W]hen we realize the almost infinite melodic possibilities of the 5-note scale, as exemplified in Celtic folk-music... we can readily understand that singers felt no urgent necessity to increase the number of notes in the octave. A further development in this direction was, however, eventually achieved by the folk-singer, though, for a long while, as was but natural, the two meidal notes required to complete the scale were introduced speculatively and with hesitation. There are many instances in Irish folk-music, for example, in which the pitch or intonation of these added sounds is varied in the course of one and the same tune. This experimental and transitional period, however, eventually came to a close and the final stage was reached, so far as the folk-singer was concerned, when the diatonic scale, i.e. the 7-note scale represented by the white notes of the pianoforte, became definitely settled... But even then, and for a long time afterwards, the mediate sounds remained 'weak' and were employed only as auxililiary notes or connecting links, rather than structural or cadential notes, so that the gaps, though covered up, were not concealed. And it was left to the art-musician to take the final step and evolve the 7-note scale of which every note could be used with equal freedom and certainty." —Cecil Sharp.

Cecil Sharp Pentatonic Mode chart

Cecil Sharp's Pentatonic Mode chart, from English Folks Songs from the Southern Appalachians. Sharp analyzed hundreds of tunes from the Southern Appalachian region of the US, identifying them as pentatonic, hexatonic and heptatonic.

Pentatonic tunes are further broken down into modes similar to those of their diatonic scale cousins, except the modes are identified by numbers, not names, and there are only five notes. The pentatonic tunes of this region were charted as missing the third AND the seventh tone in Mode 1, as opposed to the standard Western pentatonic scale which skips 4 and 7.

The hexatonic tunes of this region, the 6-tone tunes, were identified as having either the third OR the seventh tone missing in Mode 1. If the seventh is present, it may be a half or a whole tone above the preceding tone.

The heptatonic tunes of this region wer identified as having a seventh tone that in Mode 1 might be a half or a whole tone above the preceding tone.


Simon Bennett, Ravenspiral Gide to Music Theory.

David Brody, Fiddler Fakebook, Oak Publications, 1992.

Campbell and Sharp, English Folks Songs from the Southern Appalachians,

Scales, Harmonies and Modes,

Beth Isbell, A Simple Way to Understand Modes for Guitar, web,

A Beginner Guide to Modal Harmony, web,

Brendan Taaffe, Caomimhin O Raghallaigh: Irish Music at a Local Level, Web,

Diatonic scale, Wikipedia.

Pentatonic scale, Wikipedia.

Pitch Constellations are an efficient way to diagram scale, chord and mode degrees using a diagram similiar to a 12-hour clock face. Wikipedia.

The Movable-do-Solfége system allows the musician to sing a song without knowing the words; handy for memorization practice. The 'movable' in description means: DO is the tonic note of the song, not C.
Movable Do Solfége
1 Do C
  Raised 1 Di C#
  Lowered 2 Ra Db
2 Re D
  Raised 2 Ri D#
  Lowered 3 Me (or Ma) Eb
3 Mi E
4 Fa F
  Raised 4 Fi F#
  Lowered 5 Se Gb
5 Sol G
  Raised 5 Si G#
  Lowered 6 Le (or Lo) Ab
6 La A
  Raised 6 Li A#
  Lowered 7 Te (or Ta) Bb
7 Ti B

From Solfége,

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Last updated Jan 2021
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