Definition of a note
When we pick a string, say a word or clap our hands we create energy that is transmitted through the particles of matter, the air, for example. When it reaches our eardrums, we hear a sound. This movement of energy has its moments of maximum air pressure - compression and minimum air pressure - rarefaction. Therefore, it is a wave.
Like other types of waves, the sound wave has characteristics such as wavelength, amplitude and frequency. The wavelength defines the duration of a sound. The loudness of a sound depends on the amplitude of its wave. The frequency is the number of compression-rarefaction cycles that occur per second. It allows us to distinguish pitches from noise .
When we talk about musical pitches we have in mind sound waves with specific frequencies. A higher pitch has a greater frequency. Systematized pitches have names and symbols. They are called music notes. The pitch letter names are C, D, E, F, G, A, B.
Definition of an interval
An interval is a relation between two notes or, in other words, the ratio of their frequencies. Named intervals are the following: unison, second, third, fourth, fifth, sixth, seventh and octave. We can also define an interval as the distance between two notes. We can count this distance with whole steps (tones) and half steps (semitones).
When two notes appear together , they form a harmonic interval. When one note appears after the other , the two form a melodic interval. If the distance between two notes larger than an octave, we say it is a compound interval. Compound intervals are equivalents to the regular intervals only an octave higher.
Intervals from C (sharp)
Intervals from C (flat)
Compound intervals from C (sharp)
Compound intervals from C (flat)
Intervals have different types of quality: perfect, major, minor, diminished and augmented. Depending on their ratio, intervals can be consonant or dissonant. Intervals ratio with lower integers is more consonant than one with higher integers. The consonant intervals are the following: perfect unison(1:1), octave(2:1), perfect fifth(3:2), perfect fourth(4:3), major sixth(5:3), major third(5:4) and minor third(6:5), minor sixth(8:5). The dissonant intervals include major second(9:8), major seventh(15:8), minor seventh(16:9), minor second(16:15), diminished fifth(25:18) and augmented fourth(45:32). If a perfect fourth is between the bass voice and any of upper voices , it is a dissonant interval. But if a fourth is between upper voices , it is a consonant interval. Dissonant intervals sound harsh and must be resolved while consonant intervals are stable and can exist independently.
Consonant intervals from C
Dissonant intervals from C
Notes and intervals on the guitar
Standard tuning of the guitar consists of the following notes: E4 with a frequency of 329 Hz; B3 with a frequency of 247 Hz; G3 with a frequency of 196 Hz; D3 with a frequency of 147 Hz; A2 with a frequency of 110 Hz; E2 with a frequency of 82 Hz. The distance between two neighbor frets of the guitar is a half step. So twelve guitar frets represent twelve pitches of the chromatic scale. And the twelfth fret represents an octave. On the guitar, the same note, as well as the same interval can be played at several different strings and frets. The first (e) and the second (B) strings are separated by a perfect fourth. The third (G), fourth (D), fifth (A) and sixth (E) strings are also separated by a perfect fourth interval. But the second (B) and the third (G) strings are separated by a major third interval.
Intervals on the same string
The following shapes work for any string of the guitar and any fret.
Intervals on two strings
These shapes work for E and A, A and D, D and G, B and e strings because they are all separated by the same interval - a perfect fourth.
Intervals on G and B strings
The shapes work for G and B strings because they are separated by a major third.
Intervals across one string
These shapes work for E and D, A and G strings because they are separated by a minor seventh.
Intervals on D and B strings
The following shapes work for D and B, G and e strings because they are separated by a major sixth.