What is "transposition" in a musical context?

Transposition in music refers specifically to the process of shifting a piece of music from its original key to a different key. This is accomplished by maintaining the same intervallic relationships between notes, ensuring that the musical structure remains consistent even though the pitch of the notes changes. This technique is often used to accommodate a vocalist's range or to suit a specific instrumental configuration, making the music more accessible for different performers or ensembles.

The other options address different aspects of music but do not pertain to transposition. Changing the tempo affects the speed at which music is played, modifying lyrics deals with the textual component of a song, and altering dynamics involves changing the volume levels of the music rather than shifting its pitch. Thus, these choices do not capture the essence of what transposition entails.