The 7 key elements create an artistic statement to the sounds of a song. Each of the elements shape the flow and impact of the song.
The pitch focuses on the sounds - high and low - which gives the emotional touch
The melody gives an identity to the song
Harmony adds emotion through different notes
Rhythm gives the energy that makes you want to dance or reflect
Timbre is important because each instrument add its own note, color
Structure keeps the song organized to make sure it flows
Silence adds everything else that a song needs space, impact, etc.
All in all, the 7 elements work together in harmony to create a magical musical experience.