Since the human ear is a highly trainable organ, it is preferred to use a tuning fork A440 instead of any electronic tuners, enabling you to develop a good sense of pitch, to avoid tuning by a display instead of by the actual sound of your guitar. The numbers of the tuning fork, invented by John Shore in 1711, represent the Hertz (Hz) or cycles per second made by the sound wave when the fork is vibrating. To accurate tune your flamenco guitar in intervals of fourths, to the most common EBGDAE tones from treble to bass, play a 5th fret harmonic of the 5th string to match the tuner fork A440 pitch, becoming the reference for the other strings. Tuning by harmonics gives a very precise tuning, using pure intervals (fourths) to create a more resonant, vibrant sound, cutting string overtones and leaving a clear, easy to hear pitch. To play a harmonic, touch the string very lightly on the fret, not holding it down, pluck the string while release your left hand finger on the string. To tune the 4th string, match the 5th fret harmonic of the 5th string with the 7th fret harmonic of the 4th string. The low E string is tuned by matching the harmonic of the 5th fret of the 6th string to the harmonic at the 7th fret of the 5th string. The G string is tuned in the same way, matching the 7th fret harmonic of the higher string to the 5th fret harmonic of the lower string. To tune the 2nd string, match the open B string to the harmonic at the 7th fret of the 6th string. The high 1st E string is again tuned to the 2nd B string by using the 5th fret/7th fret harmonics.