3 reasons why guitarists should know intervals

1. It's good for training your musical ear

Can you tell the difference between a minor third and a major third, a minor chord and a major chord? Your ear can be your main trump card, especially if you don't care about notes, it's essential for learning chords. Try playing Pink Floyd's "The Wall" in D major instead of D minor and you will know what I am talking about. There are mistakes that you can get away with in music, but this one is unforgivable. The sooner you hear the difference, the less you'll be messing it up.

2. It helps you remember and transpose the accompaniments

Have you heard about the Nashville notation system? You can memorise that the blues goes E7, A7, E7, B7 A7, or you can learn that it's a I - IV - I - V - IV song. If you write it down this way, you can easily shift to any key which the singer (who smokes too many/few cigarettes, sleeps/doesn't sleep, etc.) wants—right on the concert stage, of course. If you learn what a fourth and a fifth are in D major, you will get it faster.

3. It is an inspirational tool for improvisation

Each of the intervals has its own colour and imprint in musical styles. The most well-known is the difference between minor and major thirds—minor (sad) vs. major (happy). Blues, on the other hand, can make nice use of the sixth (sounds "dreamy" to me), funk just wouldn't do without the X9 chord, the ninth (James Brown chord), and Hendrix wouldn't be what he is without the E7#9.

 If you swap major and minor chords, it may sound like this...

Basic terminology

An interval is the distance between the tones in a scale. Put simply, an octave comprises eight tones and the distances between them are marked as follows (in the C major scale): C - C (first), C - D (second), C - E (third), C - F (fourth), C - G (fifth), C - A (sixth), C - B (seventh), C1 - C2 (octave). What is interesting above the octave is the ninth (C1 - D2); in jazz, we can also see elevenths and thirteenths, but more about that another time.

How to start learning intervals in three points

1. Associate intervals with something familiar to you (small second—see for example Jaws).
2. Practice regularly (ear/interval training apps are easy to find; there are many and I prefer EarMaster).
3. Sing the intervals as you play, even quietly.

These few guidelines are for life, and it's not rocket science, so don't let it throw you off. At first, try the thirds (minor and major) and the sevenths (minor and major). These are the crucial intervals that create the mood and harmonic texture of the piece. In other words, to make mistakes with them is fatal, avoid it.