Dropped C is octave down to C (5th string 3rd position)
Tuning down ur guitar half a step down mens that each string is with a semi tone down -- 1st string -- Eb
2nd -- Bb 3rd-- Gb and so on. To tune you guitar that way tune 1st string to sound the same as 2nd string 4th position and once you tune 1st str that way tune all the others with respect to it. Or you may just use a the gift of civilazation called tunner.
I hope that I'v understood the matter correctly.
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