Interval Naming

Background

 

Our system of music notation is built around the seven note scale a group of pitches arranged from high to low covering one octave. The system for naming intervals uses the scale degree number and a qualifier. For example, Major 3rd (M3) or Perfect 5th (P5). Intervals of the Major scale use the qualifiers Major and Perfect and the scale degree number as shown in the diagram below.

 

 

This diagram shows the intervals of the Major scale built above C using the C Major scale:

 

Perfect intervals have a special quality of sound. They are the P1 (unison or prime), P4, P5, and P8 (octave an interval with the same note names but twelve half steps higher or lower). Major intervals are the M2, M3, M6, and M7.

 

 

This next diagram shows the intervals of the Major scale built on a single string with 12 frets:

 

 

 

The Major and Perfect intervals of the Major scale name only seven intervals plus the octave. Additional qualifiers are needed to name the other intervals. They are minor, diminished, and Augmented.

 

When Major intervals get smaller by one half step, they become minor intervals. The minor intervals, m2, m3, m6, and m7 are one half step a semitone, the octave is divided into twelve half steps smaller than their Major counterparts, M2, M3, M6, and M7.

 

When Perfect intervals are reduced in size by one half step, they become diminished. For example, the interval 1) the distance between two pitches 2) two notes combine to form an interval one half step smaller than the P5 is the diminished 5, dim 5.

 

When Perfect or Major intervals increase in size by one half step they become Augmented. For example, the interval one half step larger than the P4 is the Augmented 4th, Aug 4.

 

The Aug 4 and dim 5 have six half steps or three whole steps (six semitones or three tones). Another name for this interval is the tritone, TT.

 

The following diagram shows the twelve half steps within the octave. The Major scale is shown with its tetrachords. At the bottom of the diagram are names for the intervals that are between the intervals of the Major scale.

 

 

 

 

How to Name Intervals

 

Determining the correct name of an interval is a two step process. First, obtain the number by either counting the lines and spaces on the staff or by counting letter names. Second, count the number of half steps to determine the correct qualifier.

 

For example, what is the interval C to E?

 

First, count the letter names: C, D, E, 1,2,3 (there are 3 letter names), or count the lines and spaces:

 

This means that it is a 3rd.

 

Second, count the half steps: C-C# 1, C#-D 2, D-D# 3, D#-E 4. There are four half steps. What type of 3rd has 4 half steps? Looking at the diagram above or looking at the instrument diagrams, it is clear that this is a Major 3rd.

 

With C to Eb or with C# to E we still count three letter names or three lines and spaces on the staff. We know that these intervals are also 3rds. However, when we count the half steps, we find that there are only three. One less than the Major third. This means that we have the interval of the minor 3rd.

 

What is the interval F to G#?

 

First count the letter names: F, G, 1,2. We know that it is a 2nd.

 

Next, count the half steps: F to F# 1, F# to G 2, G to G# 3. What kind of second has three half steps. A Major 2nd has two, so this interval is larger than the M2. It is an Augmented 2nd, Aug 2. Even though it has the same number of half steps as the minor 3rd, it is not a 3rd because it only has two letter names.

 

 

Augmented 2nd

 

The Augmented 2nd sounds the same as the minor 3rd. However, the way that they are written gives them two different names.

 

minor 3rd

 

The number of half steps alone will not always yield the correct interval name. The letter names that are used to name the notes or the way that it is written on the staff must be taken into account.

 

The following table shows how to select the correct interval qualifier:

 

two half steps smaller

one half step smaller

Interval Type

one half step larger

diminished

minor

Major

Augmented

 

diminished

Perfect

Augmented

 

Use the interval objectives in MusicGoals to develop fluency reading and playing intervals. Mastery of interval reading will greatly improve sight-reading skills and is one of the essential fundamentals of music theory.

 

see also: Half Steps, Tetrachord and Scale, Keyboard Name Intervals, Keyboard Play Intervals,

Staff Name Intervals, String Name Intervals, String Play Intervals