How can I transpose a key in music?

To transpose a key in music, you need to change all the notes in a piece of music to a different key. This involves shifting all the notes up or down by the same interval. For example, if you want to transpose a piece from the key of C major to the key of G major, you would move all the notes up by a perfect fifth. This changes the overall pitch of the music while maintaining the same relationships between the notes.