Boss Chromatic Tuner TU-2 Owner's Manual page 19

2. If the tuner is not on (CHECK should be
lit), press the pedal to turn it on.
3. Play a single note on your instrument.
The string number closest to the pitch of
the input sound will appear in the note
name / string number indicator, and the
meter will indicate the pitch deviation.
(String number display)
1st string G
3rd string A
LoB (5th string) B
4. Tune your instrument.
2nd string D
4th string E
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