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How Acoustic Guitars Work


Tempered Scale

Over time, most of the musical world came to agree on a scale called the tempered scale, with the A note set at 440 Hz and all of the other notes tuned off of that. In the tempered scale, all of the notes are offset by the 12th root of 2 (roughly 1.0595) instead of the fractions we saw above. That is, if you take any note's frequency and multiply it by 1.0595, you get the frequency for the next note. Here are three octaves of the tempered scale:

  • 82.4 E - open 6th string
  • 87.3 F
  • 92.5 F#
  • 98.0 G
  • 103.8 G#
  • 110.0 A - open 5th string
  • 116.5 A#
  • 123.5 B
  • 130.8 C
  • 138.6 C#
  • 146.8 D - open 4th string
  • 155.6 D#
  • 164.8 E
  • 174.6 F
  • 185.0 F#
  • 196.0 G - open 3rd string
  • 207.6 G#
  • 220.0 A
  • 233.1 A#
  • 246.9 B - open 2nd string
  • 261.6 C - "middle C"
  • 277.2 C#
  • 293.6 D
  • 311.1 D#
  • 329.6 E - open 1st string
  • 349.2 F
  • 370.0 F#
  • 392.0 G
  • 415.3 G#
  • 440.0 A - 5th fret on 1st string
  • 466.1 A#
  • 493.8 B
  • 523.2 C
  • 554.3 C#
  • 587.3 D
  • 622.2 D#
  • 659.2 E - 12th fret on 1st string

As you can see in this table, we have finally been able to get the discussion back to guitars! This is how a guitar is tuned. A guitar with 12 clear frets has a range of three octaves, as shown above. The open sixth string is the lowest note, and the 12th fret on the first string is the highest. Here is the actual layout of all of the notes on a guitar.


You can see in this diagram that there are 72 fret positions, but the table above shows only 37 unique notes. Therefore you have multiple ways to finger identical notes on a guitar. This fact is frequently used to get all of a guitar's strings tuned. For example, you can tune A on the first string (5th fret) to 440 Hz. Then you know that E at the 5th fret on the second string is the same as the open first string, so you match those two notes up by tuning the second string. Similarly:

  • The 4th fret on the 3rd string (B) is the same as the B on the open 2nd string.
  • The 5th fret on the 4th string (G) is the same as the G on the open 3rd string.
  • The 5th fret on the 5th string (D) is the same as the D on the open 4th string.
  • The 5th fret on the 6th string (A) is the same as the A on the open 5th string.

Once you have all of the strings on a guitar perfectly tuned, using 440 Hz for A as the primary note, then the guitar will have notes with the frequencies shown in the table above, and it is said to be tuned to "concert pitch."