When a piece contains mainly notes from a minor scale, it is said to be in a minor key. The following example is in the key of E minor. You will notice that this piece has a sadder sound than those written in major keys. This sad quality is a characteristic of minor keys. Notice also that the key signature, consisting of one sharp (F#), is identical to the key signature of G major. When two keys share a key signature, they are called relative keys.