Power chords are also called root-fifth or fifth chords because they use the root note and 5th note of a scale. Another way to refer to the B power chord is B5.
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B5 Chord, power chord on 6th string |
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B5 Chord, power chord on 5th string |
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B5 Chord, power chord on 4th string |
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B5 Chord, power chord on 3rd string |