Originally Posted By: Notes Norton

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Putting the capo on makes the guitar sharp by pushing the string between two frets. Then when you put your finger down between another two frets, that string goes even sharper.



I use a capo sometimes for recording, and as rockstar_not pointed out it has nothing to do with not being able to play the chords, it has to do with getting the open voicing which for some material is very important.

Pitch is not an issue, I just tune the guitar slightly flat so that when I put the capo on it is in perfect tune.