The sound of a guitar note reflects how frequently its guitar string vibrates back and forth in a second. A frequency of 100 times a second, say, is referred to as 100 Hertz (Hz)). We’re using pitch and note to refer to sounds. Notes have names to identify them (C, D, ..)? while pitches use frequencies.

Adjacent frets on the same string are positioned to create frequencies that differ by a precise amount known as the semitone. At 12 frets apart on the same string, they create frequencies an octave apart (meaning the higher frequency is double the lower). In this case, the two notes sound very similar, very strongly related.

This results in a block of 12 notes, each a semitone apart. The next 12 frets on the same string repeat these notes, all an octave higher. (You can visualise piano as a giant guitar string, with each piano key corresponding to a fret. A piano provides several octaves of 12 note blocks)

The semitone

If you’re interested, this number comes from mathematics. It’s value is 1.059. For example, on a 6-string guitar in standard tuning, the 5th fret on the first (treble) string is usally tuned (with a tuner or pitch fork) to a frequency of 440 Hz. As a result, the 6th fret on that string produces a frequency of 440 x 1.059.

Imagine this scenario.

Two friends, Pete and Sarah jam together. Sarah knows about semitones on piano and on one guitar string.

Sarah invents a short melody on piano. She doesn’t know the names of the notes, so she decides to number the piano keys used, using zero for the lowest pitched note. She writes these numbers down (the semitones from the lowest note) to remember the melody. She uses spacing to clumsily indicate when each note is played.

0 2 4 0? 0 2 4 0? 4? 2 0? 9 ? 7 ? 0

She plays the melody to Pete. On guitar, he tries different notes to match with the note 0. He finds a match at fret 3 on the bass string. He doesn’t know about semitones.

How does Sarah explain where to locate the melody notes to Pete?

Learning note names

This is important, but mainly to orient yourself on instrument. Most improvisers never think of every note name played. This will be discussed more later.

The twelve notes of Western music can be created? with a block of twelve adjacent piano keys. Piano can create several octaves of these. We can identify (hence locate) a note by? a number 0 to 11, which is the semitone difference (distance) with the lowest pitch in the block. Notes with the same number in different blocks have the same note name. The sounds of notes with the same number in two adjacent blocks are a octave apart. We saw the same idea on one string of a guitar, using twelve adjacent frets. We saw a melody can be clumsily described using block numbers. This can’t describe accurately when each note is played. Using semitones, we can start describing musical concepts before note names are known.