intervals on the guitar/bass

The last post here dealt with seeing the intervals on the piano. This time we're going to look at the intervals on the guitar/electric bass.

If we stick with a single string it's a very straightforward affair: every fret up or down is a semi-tone, aka a minor 2nd. Here's a chart that shows all of the intervals up to (and including) the octave. The left side of the vertical line -- which represents the string, any string -- is how many frets one is measuring from any starting point; to the right side is listed the corresponding interval.

In this chart m = minor, M = major, P = perfect and TT = tritone (augmented 4th/diminished 5th).

So let's take an example: say we're interested in knowing what the interval is when we play a note on the 4th fret and (on the same string) the 11th. Just subtract the lower number from the higher -- which gives us 7 -- and consult that number on the left hand of the chart. Then look at the right hand side for the interval, which in our case is a P5.

Now, an interval like the P5 on the guitar is usually much easier to play using 2 strings. The following will apply completely to the bass and almost completely to the guitar. "Almost" because one of the strings (the B string) is not tuned like the others. For now let's just stick with the first 4 strings on the guitar (E, A, D, G).

The strings are tuned in Perfect 4ths. Consulting our chart that means that if we move from one string to the next (from left to right) we're moving 5 frets. Let's call this movement lateral movement. If we moved laterally 2 strings away we would have moved 10 frets. Actually we all know this because this is how we first started tuning the guitar/bass.

So take the following example:


What is this interval? We've gone up 2 frets and over laterally one string. That lateral move is equivalent to 5 frets, so we've actually gone up in pitch 2 + 5 = 7 frets, which according to our chart way up above is a P5.

Here's another example:


Again, this isn't hard to determine. We've traveled "up" 1 fret and laterally 2 strings, each string being equal to 5 frets. So our total distance is 1 + 5 + 5 = 11. And that corresponds to a M7.

Now let's throw a little wrench in the gears. Consider this interval:


Here we actually have to employ the concept of negative numbers, which really means that we subtract instead of add. Why? Because relative to our starting position we're going in the opposite direction. Here we've moved laterally one string and down the neck (up in the diagram) 2 frets. That is numerically 5 frets + -2 (or just 5 - 2) = 3 frets. Our chart tells us that 3 frets is a minor 3rd.

Let this sink in: next time we'll tackle that B string...