the flat or sharp signs which immediately follow the clef sign, and indicate the key in which the music is to be performed. In traditional Baroque, Classical and Romantic music, the key signature indicates a major key and its relative minor, since they have the same key signatures.
In sharp signatures, the major key can be identified by looking for the note which is half a step higher than the last sharp. The relative minor is a minor third lower than the major key.
In flat signatures, the major key can be identified by looking for the flat before last, and going down a minor third for the relative minor.
