Which version of Logic exactly are you using???
The manual you will find info about the Tuner in is the:
Logic Studio Effects PDF.
You can tune instruments connected to your system with the Tuner utility. This ensures that your external instrument recordings will be in tune with any software instruments, samples, or existing recordings in your projects.
Precision button Graphic tuning display
â€¢ Precision button: In Logic, the Graphic tuning display defaults to a linear scale. Enable the Precision button to change the scaling so that it stretches outwards from the center. This parameter is not available in MainStage.
â€¢ Graphic tuning display: Indicates the pitch of the note in the semicircular area around the Keynote/Octave displays. At the centered (12 oâ€™clock) position, the note is correctly tuned. If the indicator moves to the left of center, the note is flat. If the indicator moves to the right of center, the note is sharp.
The numbers around the edge of the display show the variance, in cents, from the target pitch. The range is marked in single semitone steps for the first 6 semitones (sharp or flat). Thereafter, larger increments are shown.
Tuning adjustment slider and field
â€¢ Keynote/Octave displays: The upper, Keynote display shows the target pitch of the note being played (the closest tuned pitch). The lower, Octave display indicates the octave that the incoming note falls into. This matches the MIDI octave scale, with the C above middle C displayed as C4, and middle C displayed as C3.
â€¢ Tuning Adjustment slider and field: Sets the pitch of the note used as the basis for tuning. By default, the Tuner is set to the projectâ€™s Tuning parameter value. Drag the knob to the left to lower the pitch corresponding to A. Drag the knob to the right to raise the pitch corresponding to A. The current value is displayed in the field.
To use the Tuner
1 Insert the Tuner into an audio channel strip.
2 Play a single note on the instrument and watch the display. If the note is flat or sharp (of the Keynote), the segments to the left or right of center are illuminated, indicating how far in cents the note is off pitch.
3 Adjust the tuning of your instrument until the indicator is centered in the graphic tuning display."
Hope that helps,