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Lesson #31: Intervals

by Tyler de Witt posted on 1999-10-18
Topic: Theory Subtopic: General
Level: Beginner Number of Readers: 73563

Intervals

A musical interval is the distance between two notes. The distance is measured in units called 'semitones'. A semitone is the smallest interval. In the sequence we learned in the lesson 'Note Names':

A A# B C C# D D# E F F# G G#

The interval between any two consecutive notes is a semitone. For example, the interval between A and A# is a semitone, the interval between C# and D is a semitone, and the interval between B and C is a semitone. Since there are no notes between any of these consecutive note names, this is the smallest interval, and this is why we use it to measure the other intervals.

A 'tone' is an interval that is equal to two semitones. For example, the interval between A and B is a tone, the interval between E and F# is a tone and so on.

Now we're going to mess you up. Really, there are other names for the intervals 'semitone' and 'tone', which will be presented shortly. First we have to take a look at how we name intervals. Consider the following sequence:

A B C D E F G A

Don't worry about the notes in-between for now. The interval between any two consecutive letter names is called a 'second'. So from A to B is a second. The interval between two notes with an extra one in-between is called a 'third'. So from A to C is a third. This continues as shown in this chart:

A to A(same note)	unison
A to B			second
A to C			third
A to D			fourth
A to E			fifth
A to F			sixth
A to G			seventh
A to A(higher A)	octave

Remember that this doesn't just apply for just the A note, the interval between B and D# is also a third, and the interval between C# and F# is a fourth, and so on.

Now we're going to look at the 'quality' of intervals. Not all seconds, or thirds, or fourths are the same. There are different kinds of seconds. A second can be 'major' or 'minor'. To distinguish between the two, we must count their semitones. This is why we first learned what a semitone was. Consider the following:

From A to B is a second.
There is one note in-between A and B, called either A# or Bb.
Therefore there are 2 semitones(or a tone) between the notes A and B.
Therefore it is said to be a 'major' second.

Consider also the following:

From A to Bb is a second. (because it is two consecutive letter names, even if one's a flat)
There are no notes between A and Bb.
Therefore there is 1 semitone between the notes A and Bb.
Therefore it is said to be a 'minor' second.

Is this starting to make sense? Like it said at the top of this lesson, intervals are named by the number of semitones between them. Also, getting back to what we said about the different names for 'semitone' and 'tone':

A major second is equal to a tone.
A minor second is equal to a semitone.

So those are the two names given to the same interval.

Now that you've seen that there are major, seconds and minor seconds, you're probably thinking that there are also major third and minor thirds. You're absolutely right. Consider the following:

From A to C# is a third.
There are 3 notes in-between A and C#. They are: A#, B and C.
Therefore there are 4 semitones between A and C#.
Therefore it is said to be an interval of a major third.

From A to C is a third.
There are 2 notes in-between A and C#. They are A# and B.
Therefore there are 3 semitones between A and C.
Therefore it is said to be an interval of a minor third.

You might notice something now. Minor intervals are smaller than major intervals(they contain less semitones). This of course only applies if you are talking about the same degree of interval. For example, a minor third is smaller than a major third, but a minor third is still bigger than a major second.

For now, don't worry about memorizing the number of semitones in each interval, a chart will be provided at the end of this lesson.

Moving on to the interval of a fourth, things change. There are no major or minor fourths. The qualities that can be applied to a fourth are 'perfect', 'diminished', and 'augmented'. A perfect fourth contains 5 semitones, as in C to F. An augmented fourth contains 6 semitones, as in C to F#. A diminished fourth contains 4 semitones, as in C# to F. From this, we can see that diminished intervals are smaller than perfect intervals, and perfect intervals are smaller than augmented intervals.

The qualities of 'perfect', 'diminished' and 'augmented' are only applied to fourths, fifths. Octaves and unisons have only one quality, and that is perfect.

All the intervals follow the same scheme as what we looked at in the examples, so I won't go over the rest. But I will make a chart here that tells you the number of semitones between each interval. You might notice that some have the same number of semitones, but are named different intervals. You're right. Some intervals have two names.

Interval:		# of semitones:	Symbol	Example:

perfect unison		0			p1	C to C
minor second		1			m2	C to C#
major second		2			M2	C to D
minor third		3			m3	C to Eb
major third		4			M3	C to E
diminished fourth	4			dim4	C# to F
perfect fourth		5			p4	C to F
augmented fourth	6			aug4	C to F#
diminished fifth	6			dim5	C to Gb
perfect fifth		7			p5	C to G
augmented fifth		8			aug5	C to G#
minor sixth		8			m6	C to Ab
major sixth		9			M6	C to A
minor seventh		10			m7	C to Bb
major seventh		11			M7	C to B
perfect octave		12			p8	C to C(the next highest C)

The things to remember from this lesson are:

1. An interval is the distance between two notes.
2. The distance is measured in semitones, which is the smallest unit.
3. Intervals are named first according to degree, which makes reference to the number of consecutive letter names between the two. Example: C to D is a second, C to E is a third, and so on.
4. The degree of the interval is given a quality. For 2nds, 3rds, 6ths, and 7ths, the qualities are either major or minor. For 4ths and 5ths, the qualities are diminished, perfect or augmented. For octaves and unisons, the only quality is perfect.
5. In the future, try to memorize all the intervals and the number of semitones between them. Don't do this for 10 years before moving to the next lesson, just learn a few, and keep working on it gradually.


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