Understanding intervals

This isn't something you need to learn right at the beginning, but sooner or later you'll need it. It's about knowing the "correct" terminology for the distance between two notes.

If you're a self-taught guitarist like me, you very likely think in terms of "up three frets", "next string up and two frets back", etc. That works fine - but if you persevere with jazz, there'll come a time when you need to talk about music with other musicians, including non-guitarists. If they know some music theory, they'll use the official terminology - and you'll look stupid if you don't know what they're talking about.

For those who prefer not to read long explanations, I'll cut to the chase. Here's a table showing the interval names and what they mean in frets:

  Interval     Frets  
min 2nd 1
maj 2nd 2
min 3rd 3
maj 3rd 4
perf 4th 5
aug 4th 6
dim 5th 6
perf 5th 7
aug 5th 8
min 6th 8
maj 6th 9
min 7th 10
maj 7th 11
octave 12


OK, and now for those who do like explanations: Our western music theory has evolved over more than a thousand years, and some of the terminology is as arbitrary and illogical as a medieval European street plan. But I'll do the best I can!

For reference, here's a fretboard diagram showing the C major scale on the 2nd string:


Intervals are named by counting the notes in the major scale from the start note to the one you're going to, including both start and target in the count. So far example, from C to F you count C-D-E-F = 4 notes, so this is a 4th. F to B is also a 4th. C to D is a 2nd, as is E to F. C to B is a 7th. You get the idea. C 1st fret to C 13th fret could be called an 8th, but it's always referred to as an octave.

If you're paying attention, you'll have noticed that the intervals don't always correspond to the same number of frets. C to D is a 2nd, so is E to F, yet C to D is 2 frets and E to F is 1 fret. This difference is denoted with major and minor. C to D is a major 2nd, E to F is a minor 2nd. C to Db is also a minor 2nd. C to B is a major 7th, C to Bb is a minor 7th, etc.

The intervals of a 4th and a 5th are treated differently: for historical reasons that I won't go into, these are referred to as "perfect" intervals. There's no such thing as a major or minor 4th or 5th. The interval between the 4th and 5th can be referred to as an augmented 4th or a diminished 5th. For example: F-G-A-B is a 4th, B-C-D-E-F is a 5th, yet both are 6 frets. So the former is an aug 4th, the latter is a dim 5th. But this isn't so important - most jazzers just call it a tritone, because 6 frets = three whole tones.

You can use the same naming system for intervals greater than an octave. The list continues upwards with min 9th, maj 9th, etc.

Intervals can be used going downwards as well as upwards. From C up to A is up a maj 6th, from C down to A is down a min 3rd. From E up to F is up a min 2nd, from E down to F is down a maj 7th. From C up to G is up a perf 5th, from C down to G is down a perf 4th. Note the pattern: when inverting intervals, maj becomes min, min becomes maj, perf stays perf, and the numbers always add up to 9.