Simplify the following text for a Grade 12 native English-speaking person.
Original: Whereas traditionally key signatures were canceled whenever the new key signature had fewer sharps or flats than the old key signature , in modern popular and commercial music , cancellation is only done when C major or A minor replaces another key .
Simplified: Most of the time key signatures were canceled whenever the new key signature had fewer sharps or flats than the old key signature , in modern popular music , this is only done when C major or A minor replace another key .