Guitar Intonation Tuning at the Bridge / Base of Strings

Guitar intonation adjustment at the bridge (the base of the strings, opposite the headstock/neck) is one of the most important parts of setting up a guitar for accurate tuning. Here’s a breakdown:

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1. What “intonation” means

• Intonation is whether a guitar plays in tune all the way up the neck.
• A guitar string is not perfectly flexible; its stiffness, tension, and length cause slight tuning errors when fretted.
• Even if the open strings are perfectly tuned with a tuner, the notes higher on the neck can go sharp or flat if the string length is not compensated.

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2. How the bridge adjustment works

• On most electric guitars and many acoustics with adjustable bridges, each string passes over a saddle that can be moved forward (shorter string) or backward (longer string).
• By moving the saddle, you are fine-tuning the scale length of that string so that fretted notes (especially the 12th fret octave) are in tune with the open string.
• Rule of thumb:
• If the 12th fret note is sharp, lengthen the string (move saddle back).
• If the 12th fret note is flat, shorten the string (move saddle forward).

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3. Why this compensation is necessary

• Fretting a note stretches the string slightly, raising its pitch.
• Different string gauges, action height, and playing styles change how much compensation is needed.
• Without proper intonation, chords sound out of tune the higher you play on the neck, even if the open strings are correct.

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4. Tremolo (whammy) bar and intonation

• A tremolo bridge (e.g. Fender Strat’s “whammy bar” or a Floyd Rose system) pivots the entire bridge, changing string tension so notes dip or rise.
• Intonation setup on tremolo-equipped guitars is even more critical because:
• The saddles must still be adjusted individually for accurate tuning up the neck.
• The floating bridge must be balanced between spring tension (in the back cavity) and string tension, so that after using the bar, the bridge returns to its neutral position without pitch drift.
• Tremolo systems can make intonation trickier, since any change in string gauge or tuning can throw off the bridge balance and therefore the intonation.

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5. Big picture

• Intonation adjustment ensures consistent tuning accuracy across the fretboard.
• It’s part of a proper setup along with:
• Neck relief (truss rod)
• String action (height)
• Nut slot depth
• Bridge balance (on tremolo systems)

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