The basics
Intervals
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Maj/Min 3rd, Perf/Dim 5th
In addition to the octave there are lots of other intervals. Here are some intervals that occur within an octave that are particularly important because they help in understanding chords:
The Major 3rd
The 'major 3rd' is the first note and third note of the major scale. It is useful to think how many semitones this is. If you play the note A at fret 2 on string f of your guitar, you have to count up four frets (four semitones) to get to C sharp.
The Minor Third
The 'minor 3rd' is the 1st note and the 3rd note of the major scale lowered by a semitone (actually the lowered 3rd is the 3rd note of the minor scale which will be covered later). In terms of semitones, if you play the note A at fret 2 on string f of your guitar, you have to count up 3 frets (3 semitones) to get to C.
