Why attack changes pitch
A strong pluck stretches the string sideways, increasing tension for an instant. The tuner may show a sharp attack followed by a flatter settled pitch. This effect is larger on loose low strings and aggressive drop-tuned playing.
Match your real technique
A player with a heavy stage attack may benefit from tuning the settled note slightly differently than a very light fingerstyle player. The best reference is a repeatable attack close to how the guitar will actually be played.
Where to pluck
Plucking near the middle of the vibrating string emphasizes the fundamental, while plucking very close to the bridge produces stronger upper harmonics. A clear note near the usual picking area normally works best.
Step-by-step check
- Mute the unused strings.
- Pluck once at normal practice strength.
- Ignore the first instant of the reading.
- Judge the pitch as it settles.
- Repeat with the same force after every adjustment.
Reliable tuning habits
Work with one string at a time, use a moderate and repeatable picking attack, and let the initial pitch settle briefly. Make the final adjustment by approaching the target from below so slack is taken out of the tuning post and nut. After all six strings are close, repeat the entire pass because every tension change can slightly affect the other strings.